Merge remote-tracking branch 'upstream/master'

Author: ivanlanin

.travis.yml

@@ -4,9 +4,12 @@ php:
   - 5.3
   - 5.4
   - 5.5
-  ## Wait for solving this issue : https://github.com/travis-ci/travis-ci/issues/1749
-  # - hhvm
-
+  ## @reference https://github.com/travis-ci/travis-ci/issues/1749
+  - hhvm
+matrix:
+  allow_failures:
+    - php: hhvm
+    
 before_script:
   ## Composer
   - curl -s http://getcomposer.org/installer | php