remove support for php < 7.1.3

Author: alcalyn

.travis.yml

@@ -9,17 +9,8 @@ cache:
 
 matrix:
     include:
-        - php: 5.5
-        - php: 5.6
-        - php: 7.0
         - php: 7.1
-          env: SYMFONY_DEPS_VERSION=3
         - php: hhvm
 
-before_script:
-    - sh -c "if [ '$SYMFONY_DEPS_VERSION' = '3.0' ]; then sed -i 's/~2\.8|3\.0\.\*/3.0.*@dev/g' composer.json; composer update; fi"
-    - sh -c "if [ '$SYMFONY_DEPS_VERSION' = '' ]; then sed -i 's/~2\.8|3\.0\.\*/2.8.*@dev/g' composer.json; composer update; fi"
-    - travis_retry composer install
-
 script:
     - ./vendor/bin/simple-phpunit