added phpunit to composer.json, update travis config

Author: igor-chepurnoi

.travis.yml

@@ -1,6 +1,7 @@
 language: php
 
 php:
+  - 7.0
   - 7.1
 
 # faster builds on new travis setup not using sudo
@@ -18,4 +19,4 @@ install:
 
 script:
   - vendor/friendsofphp/php-cs-fixer/php-cs-fixer fix --dry-run --diff
-  - phpunit
+  - vendor/bin/phpunit --verbose

composer.json

@@ -19,7 +19,7 @@
         }
     ],
     "require": {
-        "php": ">=7.1",
+        "php": ">=7.0.0",
         "yiisoft/yii2": "~2.0.12",
         "yiisoft/yii2-bootstrap": "*",
         "yii2mod/yii2-enum": "*",
@@ -32,7 +32,8 @@
         "yiisoft/yii2-imagine": "^2.1"
     },
     "require-dev": {
-        "friendsofphp/php-cs-fixer": "~2.0"
+        "friendsofphp/php-cs-fixer": "~2.0",
+        "phpunit/phpunit": "~6.0"
     },
     "autoload": {
         "psr-4": {