Remove php 5.6 build

.travis.yml

@@ -7,9 +7,10 @@ cache:
     - $HOME/.composer/cache/files
 
 php:
-  - 5.6
   - 7.0
   - 7.1
+  - 7.2
+  - nightly
 
 env:
   global:
@@ -19,8 +20,10 @@ env:
 matrix:
   fast_finish: true
   include:
-    - php: 5.6
+    - php: 7.2
       env: PDO=0 PHPCS_TEST=1
+  allow_failure:
+    - php: nightly
 
 before_script:
   # Init PHP