fixed Travis config for HHVM

Author: craue

.travis.yml

@@ -6,13 +6,14 @@ php:
   - 5.5
   - 5.6
   - 7.0
-  - hhvm
 
 env:
   - SYMFONY_VERSION='2.7.*'
 
 matrix:
   include:
+    - php: hhvm
+      dist: trusty
     - php: 5.3.3
       env: DEPS='lowest'
     - php: 5.6