Toggle via attribute (#5)

* Toggle functionality based on attribute value
* Updated Readme

Author: chrisswaine

README.md

@@ -19,10 +19,11 @@ Lightweight drag to scroll directive for AngularJS
 angular.module('MyApp', ['ng-drag-scroll']);
 ```
 
-* Add an attribute to an element with a scrollbar to make the content scrollable
+* Add an attribute set to true to an element with a scrollbar to make the content scrollable, setting the attribute to false will prevent drag to scroll behaviour.
+The attribute value can be set to a scope varibale to easily toggle between enabled and disabled.
 
 ```html
-<div drag-scroll>
+<div drag-scroll="true">
   <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam viverra nec consectetur ante hendrerit. Donec et mollis dolor. Praesent et diam eget libero egestas mattis sit amet vitae augue. Nam tincidunt congue enim, ut porta lorem lacinia consectetur. Donec ut libero sed arcu vehicula ultricies a non tortor. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean ut gravida lorem. Ut turpis felis, pulvinar a semper sed, adipiscing id dolor. Pellentesque auctor nisi id magna consequat sagittis. Curabitur dapibus enim sit amet elit pharetra tincidunt feugiat nisl imperdiet. Ut convallis libero in urna ultrices accumsan. Donec sed odio eros. Donec viverra mi quis quam pulvinar at malesuada arcu rhoncus. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. In rutrum accumsan ultricies. Mauris vitae nisi at sem facilisis semper ac in est.</p>
 </div>
 ```

src/ng-drag-scroll.js

@@ -12,7 +12,9 @@
         //Usage:
         //<div drag-scroll>Lorem ipsum dolor sit amet</div>
         var directive = {
-            scope: false,
+            scope:{
+                dragScroll:'='
+            },
             restrict: 'A',
             link: function($scope, $element, $attributes, vm) {
                 var allowedClickOffset = 5;
@@ -53,70 +55,78 @@
                  * @param {object} e MouseDown event
                  */
                 function handleMouseDown (e) {
-                    for (var i= 0; i<excludedClasses.length; i++) {
-                        if (angular.element(e.target).hasClass(excludedClasses[i])) {
-                            return false;
+                    if($scope.dragScroll){
+                        for (var i= 0; i<excludedClasses.length; i++) {
+                            if (angular.element(e.target).hasClass(excludedClasses[i])) {
+                                return false;
+                            }
                         }
-                    }
 
-                    $scope.$apply(function() {
-                        onDragStart($scope);
-                    });
+                        $scope.$apply(function() {
+                            onDragStart($scope);
+                        });
 
-                    // Set mouse drag listeners
-                    setDragListeners();
+                        // Set mouse drag listeners
+                        setDragListeners();
 
-                    // Set 'pushed' state
-                    pushed = true;
-                    lastClientX = startClientX = e.clientX;
-                    lastClientY = startClientY = e.clientY;
+                        // Set 'pushed' state
+                        pushed = true;
+                        lastClientX = startClientX = e.clientX;
+                        lastClientY = startClientY = e.clientY;
 
-                    clearSelection();
+                        clearSelection();
 
-                    e.preventDefault();
-                    e.stopPropagation();
+                        e.preventDefault();
+                        e.stopPropagation();
+                    }
+                    
                 }
 
                 /**
                  * Handles mouseup event
                  * @param {object} e MouseUp event
                  */
                 function handleMouseUp (e) {
-                    var selectable = ('drag-scroll-text' in e.target.attributes);
-                    var withinXConstraints = (e.clientX >= (startClientX - allowedClickOffset) && e.clientX <= (startClientX + allowedClickOffset));
-                    var withinYConstraints = (e.clientY >= (startClientY - allowedClickOffset) && e.clientY <= (startClientY + allowedClickOffset));
+                    if($scope.dragScroll){
+                        var selectable = ('drag-scroll-text' in e.target.attributes);
+                        var withinXConstraints = (e.clientX >= (startClientX - allowedClickOffset) && e.clientX <= (startClientX + allowedClickOffset));
+                        var withinYConstraints = (e.clientY >= (startClientY - allowedClickOffset) && e.clientY <= (startClientY + allowedClickOffset));
+
+                        // Set 'pushed' state
+                        pushed = false;
+
+                        // Check if cursor falls within X and Y axis constraints
+                        if(selectable && withinXConstraints && withinYConstraints) {
+                            // If so, select the text inside the target element
+                            selectText(e.target);
+                        }
 
-                    // Set 'pushed' state
-                    pushed = false;
+                        $scope.$apply(function() {
+                            onDragEnd($scope);
+                        });
 
-                    // Check if cursor falls within X and Y axis constraints
-                    if(selectable && withinXConstraints && withinYConstraints) {
-                        // If so, select the text inside the target element
-                        selectText(e.target);
+                        removeDragListeners();
                     }
-
-                    $scope.$apply(function() {
-                        onDragEnd($scope);
-                    });
-
-                    removeDragListeners();
+                    
                 }
 
                 /**
                  * Handles mousemove event
                  * @param {object} e MouseMove event
                  */
                 function handleMouseMove (e) {
-                    if (pushed) {
-                        if(!axis || axis === 'x') {
-                            $element[0].scrollLeft -= (-lastClientX + (lastClientX = e.clientX));
-                        }
-                        if(!axis || axis === 'y') {
-                            $element[0].scrollTop -= (-lastClientY + (lastClientY = e.clientY));
+                    if($scope.dragScroll){
+                        if (pushed) {
+                            if(!axis || axis === 'x') {
+                                $element[0].scrollLeft -= (-lastClientX + (lastClientX = e.clientX));
+                            }
+                            if(!axis || axis === 'y') {
+                                $element[0].scrollTop -= (-lastClientY + (lastClientY = e.clientY));
+                            }
                         }
-                    }
 
-                    e.preventDefault();
+                        e.preventDefault();
+                    } 
                 }
 
                 /**