reverted yiisoft#3109 as tests are not running

cebe · cebe · commit 200fc45173f8 · 2013-12-14T00:16:18.000+01:00
more work on that needed first.
diff --git a/.travis.yml b/.travis.yml
@@ -5,7 +5,6 @@ php:
   - 5.3
   - 5.4
   - 5.5
-  - hhvm
 
 services:
   - redis-server
