drop support for unmaintained Symfony versions (#24)

Author: xabbuh

.travis.yml

@@ -22,19 +22,20 @@ matrix:
         - php: 7.2
           env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest" SYMFONY_DEPRECATIONS_HELPER="weak_vendors"
         - php: 5.5
+          dist: precise
           env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest" SYMFONY_DEPRECATIONS_HELPER="weak_vendors"
 
         - php: 7.1
           env: COVERAGE=true TEST_COMMAND="composer test-ci"
 
           # Test the latest stable release
         - php: 5.5
+          dist: precise
         - php: 5.6
+          dist: precise
         - php: 7.0
         - php: 7.2
           dist: trusty
-        - php: 7.1
-          env: DEPENDENCIES="dunglas/symfony-lock:^2"
         - php: 7.1
           env: DEPENDENCIES="dunglas/symfony-lock:^3"
         - php: 7.1

composer.json

@@ -11,10 +11,10 @@
     ],
     "require": {
         "php": "^5.5 || ^7.0",
-        "symfony/dependency-injection": "^2.3 || ^3.0 || ^4.0",
-        "symfony/framework-bundle": "^2.3 || ^3.0 || ^4.0",
-        "symfony/http-kernel": "^2.3 || ^3.0 || ^4.0",
-        "symfony/yaml": "^2.3 || ^3.0 || ^4.0"
+        "symfony/dependency-injection": "^3.4 || ^4.3",
+        "symfony/framework-bundle": "^3.4 || ^4.3",
+        "symfony/http-kernel": "^3.4 || ^4.3",
+        "symfony/yaml": "^3.4 || ^4.3"
     },
     "require-dev": {
         "phpunit/phpunit": "^4.8.36 || ^5.5 || ^6.2"