Do not test lower then 5.6

Author: casperbakker

.travis.yml

@@ -1,8 +1,6 @@
 language: php
 
 php:
-  - 5.5.9
-  - 5.5
   - 5.6
   - 7.0
   - hhvm
@@ -11,18 +9,8 @@ env:
   global:
     - setup=basic
 
-matrix:
-  include:
-    - php: 5.5.9
-      env: setup=lowest
-    - php: 5.5.9
-      env: setup=stable
-
 sudo: false
 
-install:
-  - if [[ $setup = 'basic' ]]; then travis_retry composer install --no-interaction --prefer-source; fi
-  - if [[ $setup = 'stable' ]]; then travis_retry composer update --prefer-source --no-interaction --prefer-stable; fi
-  - if [[ $setup = 'lowest' ]]; then travis_retry composer update --prefer-source --no-interaction --prefer-lowest --prefer-stable; fi
+install: composer install --no-interaction --prefer-source
 
 script: vendor/bin/phpunit