add Symfony 4 build in travis-ci matrix

Author: fbourigault

.travis.yml

@@ -36,6 +36,8 @@ matrix:
           env: DEPENDENCIES="dunglas/symfony-lock:^2"
         - php: 5.5
           env: DEPENDENCIES="dunglas/symfony-lock:^3"
+        - php: 7.1
+          env: DEPENDENCIES="dunglas/symfony-lock:^4 'matthiasnoback/symfony-config-test:dev-master as 3.1'"
 
           # Latest commit to master
         - php: 7.1

composer.json

@@ -38,7 +38,6 @@
     "require-dev": {
         "guzzlehttp/psr7": "^1.0",
         "matthiasnoback/symfony-dependency-injection-test": "^1.1 || ^2.0 || dev-feature/symfony-4",
-        "matthiasnoback/symfony-config-test": "^2.0 || dev-master as 3.1",
         "nyholm/nsa": "^1.1",
         "php-http/buzz-adapter": "^0.3",
         "php-http/curl-client": "^1.0",