Changed the travis config to use the builtin composer

Author: stof

.travis.yml

@@ -7,9 +7,8 @@ php:
     - 5.6
     - hhvm
 
-before_script:
-    - curl -s http://getcomposer.org/installer | php
-    - php composer.phar --dev install
+install:
+    - composer install
 
 script:
     - vendor/bin/phpunit