Drop PHP 5.4 support

Author: josegonzalez

.travis.yml

@@ -1,7 +1,6 @@
 language: php
 
 php:
-  - 5.4
   - 5.5
   - 5.6
   - 7.0
@@ -23,10 +22,10 @@ matrix:
   fast_finish: true
 
   include:
-    - php: 5.4
+    - php: 5.5
       env: PHPCS=1 DEFAULT=0
 
-    - php: 5.4
+    - php: 5.5
       env: COVERALLS=1 DEFAULT=0
 
     - php: hhvm