drop HHVM support

Author: xabbuh

.travis.yml

@@ -12,7 +12,6 @@ php:
   - 5.6
   - 7.0
   - 7.1
-  - hhvm
 
 matrix:
   fast_finish: true
@@ -24,7 +23,7 @@ matrix:
       env: deps="high"
 
 before_install:
-  - if [[ "$TRAVIS_PHP_VERSION" != "hhvm" ]]; then phpenv config-rm xdebug.ini; fi
+  - phpenv config-rm xdebug.ini
   - composer self-update
 
 install: