added --prefer-source to travis

Author: vimishor

.travis.yml

@@ -10,7 +10,7 @@ matrix:
 
 before_script:
   - curl -s http://getcomposer.org/installer | php
-  - php composer.phar install --dev --no-interaction
+  - php composer.phar install --dev --prefer-source
 
 script:
   - mkdir -p build/logs