minor #885 add php 7.1 to travis (Rotzbua)

This PR was merged into the 5.x branch.

Discussion
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add php 7.1 to travis

For testing but can fail.

Commits
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efb4f59 add php 7.1

.travis.yml

@@ -21,6 +21,7 @@ matrix:
         - php: 5.5
         - php: 5.6
         - php: 7.0
+        - php: 7.1
         - php: hhvm
     allow_failures:
         - php: hhvm