travis: added PHP 7.1

Author: dg

Diff for: .travis.yml

@@ -2,12 +2,16 @@ language: php
 php:
     - 5.6
     - 7.0
+    - 7.1
 
 matrix:
     include:
         - php: 5.6
           env: dependencies="--prefer-lowest --prefer-stable"
 
+    allow_failures:
+        - php: 7.1
+
 script:
     - vendor/bin/tester tests -s -c tests/php-unix.ini $coverage
     - php temp/code-checker/src/code-checker.php --short-arrays