minor #1800 improve the Travis CI config (xabbuh)

This PR was merged into the 2.3-dev branch.

Discussion
----------

improve the Travis CI config

* drop the `minimum-stability` setting in `composer.json`
* set `minimum-stability` only when needed instead
* use `symfony/lts` instead of `symfony/symfony`

Commits
-------

a5f3ccc improve the Travis CI config

Author: xabbuh

.travis.yml

@@ -18,17 +18,21 @@ matrix:
     - php: 5.5
       env: COMPOSER_FLAGS="--prefer-lowest" SYMFONY_DEPRECATIONS_HELPER=weak
     - php: 5.6
+    # Symfony 2 LTS
     - php: 7.0
-      env: SYMFONY_VERSION='2.8.*'
+      env: SYMFONY_LTS='^2'
+    # Symfony 3 LTS
     - php: 7.0
-      env: SYMFONY_VERSION='3.4.*'
+      env: SYMFONY_LTS='^3' DEPENDENCIES='dev'
+    # development dependencies
     - php: 7.1
-      env: SYMFONY_VERSION='4.0.*'
+      env: DEPENDENCIES='dev'
 
 before_install:
   - if [ "$TRAVIS_PHP_VERSION" != "hhvm" ]; then phpenv config-rm xdebug.ini; fi
-  - if [ "$SYMFONY_VERSION" != "" ]; then composer require --dev --no-update symfony/symfony=$SYMFONY_VERSION; fi
+  - if [ "$DEPENDENCIES" != "" ]; then composer config minimum-stability $DEPENDENCIES; fi
+  - if [ "$SYMFONY_VERSION" != "" ]; then composer require --dev --no-update symfony/lts=$SYMFONY_VERSION; fi
 
-install: composer update $COMPOSER_FLAGS --prefer-dist --prefer-stable
+install: composer update $COMPOSER_FLAGS --prefer-dist
 
 script: ./phpunit

composer.json

@@ -64,7 +64,6 @@
         "jms/serializer-bundle": "^1.2|^2.0",
         "psr/http-message": "^1.0"
     },
-    "minimum-stability": "dev",
     "suggest": {
         "sensio/framework-extra-bundle": "Add support for route annotations and the view response listener, requires ^3.0",
         "jms/serializer-bundle": "Add support for advanced serialization capabilities, recommended, requires ^1.0",