Update Travis configuration to only test > php 7

Author: timoschinkel

.travis.yml

@@ -7,9 +7,9 @@ cache:
         - $HOME/.composer/cache/files
 
 php:
-    - 5.5
-    - 5.6
     - 7.0
+    - 7.1
+    - 7.2
     - hhvm
 
 env:
@@ -24,9 +24,6 @@ matrix:
     allow_failures:
         - php: hhvm
     fast_finish: true
-    include:
-        - php: 5.5
-          env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest" COVERAGE=true TEST_COMMAND="composer test-ci"
 
 before_install:
     - if [[ $COVERAGE != true && $TRAVIS_PHP_VERSION != hhvm ]]; then phpenv config-rm xdebug.ini; fi