travis: PHP 7.0 nightly added

.travis.yml

@@ -18,10 +18,15 @@ services:
 language: php
 php:
 # - "5.2" is not supported because pyrus to install PHP_Codesniffer is not available
- - "5.3"
- - "5.4"
- - "5.5" 
- - "5.6"
+ - 5.3
+ - 5.4
+ - 5.5 
+ - 5.6
+ - 7.0
+ 
+matrix:
+  allow_failures:
+    - php: 7.0
 
 env:
  - DB=mysql