Merge pull request #756 from owncloud/use-travis-docker

Use docker on travis .....

.travis.yml

+sudo: false
 language: php
 php:
   - 5.4
   - 5.5
   - 5.6
+  - 7
   - hhvm
 
 env:
@@ -58,4 +60,5 @@ matrix:
 
   allow_failures:
     - php: hhvm
+    - php: 7
   fast_finish: true