[Travis] Add composer prefer-lowest build

.travis.yml

@@ -9,7 +9,10 @@ php:
     - hhvm
     - hhvm-nightly
 
-env: SYMFONY_VERSION=2.3.*
+env:
+    global:
+        - COMPOSER_PREFER_LOWEST=false
+        - SYMFONY_VERSION=2.3.*
 
 cache:
     directories:
@@ -21,14 +24,16 @@ install:
     - composer require --no-update symfony/framework-bundle:${SYMFONY_VERSION}
     - composer require --no-update symfony/form:${SYMFONY_VERSION}
     - if [[ "$SYMFONY_VERSION" = *dev* ]]; then sed -i "s/\"MIT\"/\"MIT\",\"minimum-stability\":\"dev\"/g" composer.json; fi
-    - composer install --prefer-source
+    - composer update --prefer-source `if [[ $COMPOSER_PREFER_LOWEST = true ]]; then echo "--prefer-lowest --prefer-stable"; fi`
 
 script: bin/phpunit --coverage-clover clover.xml
 
 after_script: bin/coveralls -v
 
 matrix:
     include:
+        - php: 5.6
+          env: COMPOSER_PREFER_LOWEST=true
         - php: 5.6
           env: SYMFONY_VERSION=2.2.*
         - php: 5.6

composer.json

@@ -12,14 +12,16 @@
     ],
     "require": {
         "php": ">=5.3.3",
-        "symfony/framework-bundle": "~2.2",
+        "egeloen/json-builder": "~2.0@dev",
+        "symfony/dependency-injection": "~2.2",
         "symfony/form": "~2.2",
-        "egeloen/json-builder": "~2.0@dev"
+        "symfony/framework-bundle": "~2.2",
+        "symfony/yaml": "^2.0.5"
     },
     "require-dev": {
         "phpunit/phpunit": "~4.0",
-        "twig/twig": "~1.12",
-        "satooshi/php-coveralls": "~0.6"
+        "satooshi/php-coveralls": "~0.6",
+        "twig/twig": "~1.12"
     },
     "suggest": {
         "twig/twig": "Allows to use twig templates"