Made HHVM a allowed failure on travis.

Author: h4cc

.travis.yml

@@ -7,6 +7,10 @@ php:
   - 5.6
   - hhvm
 
+matrix:
+  allow_failures:
+    - php: hhvm
+
 env:
   - SYMFONY_VERSION=2.5.* PHPUNIT_VERSION=~3.7
   - SYMFONY_VERSION=2.0.* PHPUNIT_VERSION=~4.0