Kill PHP 5.6 support

Author: Niels Theen

.travis.yml

@@ -1,7 +1,6 @@
 language: php
 
 php:
-  - 5.6
   - 7.0
   - 7.1
   - 7.2
@@ -10,8 +9,6 @@ dist: trusty
 
 matrix:
   include:
-    - php: 5.6
-      dist: precise
     - php: 7.0
       env:
         - DEPENDENCIES=lowest