add PHP 7.2 beta to Travis build matrix

Author: Martin Hujer

.travis.yml

@@ -5,6 +5,7 @@ sudo: false
 php:
   - 7.0
   - 7.1
+  - 7.2
   - nightly
 
 env:
@@ -14,6 +15,7 @@ env:
 matrix:
   fast_finish: true
   allow_failures:
+    - php: 7.2
     - php: nightly
 
 before_install: