PHP testing matrixes update (Remove PHP5+add lowdep to travis)

Author: ek9

.travis.yml

@@ -2,12 +2,15 @@ language: php
 
 matrix:
   include:
-    - php: 5.6
-    - php: 5.6
-      env: deps=low
     - php: 7.0
+    - php: 7.0
+      deps: low
+    - php: 7.1
     - php: 7.1
+      deps: low
+    - php: 7.2
     - php: 7.2
+      deps: low
 
 before_script:
   - composer validate