Drop support for HHVM

Author: WyriHaximus

.travis.yml

@@ -11,7 +11,6 @@ php:
   - 7.0
   - 7.1
   - nightly
-  - hhvm
 
 ## Build matrix for lowest and highest possible targets
 matrix:
@@ -22,18 +21,12 @@ matrix:
       env: dependencies=lowest
     - php: nightly
       env: dependencies=lowest
-    - php: hhvm
-      env: dependencies=lowest
     - php: 7.0
       env: dependencies=highest
     - php: 7.1
       env: dependencies=highest
     - php: nightly
       env: dependencies=highest
-    - php: hhvm
-      env: dependencies=highest
-  allow_failures:
-    - php: hhvm
 
 ## Install or update dependencies
 install: