Add PHP 7 on Travis

.travis.yml

@@ -9,8 +9,13 @@ php:
   - 5.4
   - 5.5
   - 5.6
+  - 7.0
   - hhvm
 
+matrix:
+  allow_failures:
+    - php: 7.0
+
 before_script:
     - composer self-update
     - composer install --dev