Update travis to drop PHP 5.4

Author: Nyholm

.travis.yml

@@ -7,7 +7,6 @@ cache:
         - $HOME/.composer/cache
 
 php:
-    - 5.4
     - 5.5
     - 5.6
     - 7.0
@@ -24,7 +23,7 @@ branches:
 matrix:
     fast_finish: true
     include:
-        - php: 5.4
+        - php: 5.5
           env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest" COVERAGE=true TEST_COMMAND="composer test-ci"
 
 before_install: