[update] improved docs (fix error and add example action)

Author: Sergio Daniel Xalambrí

README.md

@@ -1,7 +1,8 @@
 # socket.io-redux
-Redux middleware to emit action via socket.io.
+Redux middleware to emit actions to a socket.io server
 
 ## API
+### Apply middleware
 ```javascript
 import io from 'socket.io-client';
 import { createStore, applyMiddleware } from 'redux';
@@ -11,7 +12,23 @@ import socketIO from 'socket.io-redux';
 import reducer from './reducer';
 
 const store = createStore(reducer, applyMiddleware(
-  socketIO(io.connect(process.env.NODE_ENV))
+  socketIO(io.connect(process.env.SOCKET_URL))
 ));
 ```
-* `socketIO` receive a `socket` instance created by `io.connect(url)`.
+* `socketIO` receive a `socket` instance created by `io.connect(<url>)`.
+
+### Example action
+```javascript
+const action = {
+  type: 'ADD_TODO',
+  payload: {
+    message: 'Use socket.io-redux middleware',
+  },
+  meta: {
+    socket: {
+      channel: 'add:todo',
+    },
+  },
+};
+```
+* `meta.socket.channel` define the socket.io channel to use to emit the action.