Added phpunit 4 to require-dev and using it in .travis.yml

Author: WyriHaximus

.travis.yml

@@ -14,4 +14,4 @@ before_script:
   - composer install --dev --prefer-source
 
 script:
-  - phpunit --coverage-text
+  - php vendor/bin/phpunit --coverage-text

composer.json

@@ -16,5 +16,8 @@
         "branch-alias": {
             "dev-master": "0.4-dev"
         }
+    },
+    "require-dev": {
+        "phpunit/phpunit": "4.*"
     }
 }