Added PHP 5.6 and HHVM to travis.yml

Author: Nyholm

.travis.yml

@@ -4,6 +4,12 @@ php:
   - 5.3
   - 5.4
   - 5.5
+  - 5.6
+  - hhvm
+ 
+matrix:
+    allow_failures:
+        - php: hhvm
 
 env:
     - SYMFONY_VERSION="2.1.*"