Update travis build settings

.travis.yml

@@ -4,13 +4,8 @@ sudo: false
 
 matrix:
     include:
-        - php: 5.3.3
-        - php: 5.3
-        - php: 5.3
+        - php: 7
           env: deps=low
-        - php: 5.4
-        - php: 5.5
-        - php: 5.6
         - php: 7
         - php: hhvm
     fast_finish: true