Update travis-ci config

Author: Bui Sy Nguyen

.travis.yml

@@ -1,17 +1,14 @@
 language: php
-
 php:
-  - 5.3
-  - 5.4
-  - 5.5
   - 5.6
+  - 5.5
+  - 5.4
+  - 5.3
   - 7
   - hhvm
-
 install:
   - composer self-update
   - composer global require "fxp/composer-asset-plugin:1.0.0"
   - composer install --prefer-dist --dev
   - composer info --installed
-
-script: phpunit --configuration phpunit.xml.dist
+script: phpunit -c phpunit.xml