Add php7.1 build

.travis.yml

@@ -4,9 +4,11 @@ sudo: false
 
 matrix:
     include:
-        - php: 7
+        - php: 7.0
           env: deps=low
-        - php: 7
+        - php: 7.0
+        - php: 7.1
+        - php: nightly
     fast_finish: true
 
 before_script: