Bump requirements to PHP ^7.1

.travis.yml

@@ -2,17 +2,9 @@ language: php
 
 php:
     - 7.1
-    - 7.0
-    - 5.6
-
-env:
-    global:
-        - COMPOSER_OPTIONS=""
 
 matrix:
     include:
-        - php: 5.6
-          env: COMPOSER_OPTIONS="--prefer-lowest"
         - php: nightly
     allow_failures:
         - php: nightly
@@ -26,7 +18,7 @@ before_install:
     - phpenv config-rm xdebug.ini || true
 
 install:
-    - composer update --prefer-dist $COMPOSER_OPTIONS
+    - composer update --prefer-dist
 
 script:
     - composer validate --strict

composer.json

@@ -10,7 +10,7 @@
         }
     ],
     "require": {
-        "php": "^5.6|^7.0",
+        "php": "^7.1",
 
         "behat/behat": "^3.1",
         "symfony/http-kernel": "^2.7|^3.0"