Simplified the Travis configuration

The tests against specific Symfony versions are now running only for a single PHP version to limit the number of jobs in the build matrix. They are also installing the full Symfony repo to be sure that all components are actually at the specified version without the need to require each of them explicitly.

.travis.yml

@@ -7,28 +7,24 @@ php:
   - 5.6
   - hhvm
 
-env:
-    - SYMFONY_VERSION=2.1.*
-    - SYMFONY_VERSION=2.2.*
-    - SYMFONY_VERSION=2.3.*
-    - SYMFONY_VERSION=2.4.*
-    - SYMFONY_VERSION=dev-master
-
 matrix:
+    include:
+        - php: 5.5
+          env: SYMFONY_VERSION='2.1.*'
+        - php: 5.5
+          env: SYMFONY_VERSION='2.2.*'
+        - php: 5.5
+          env: SYMFONY_VERSION='2.3.*'
+        - php: 5.5
+          env: SYMFONY_VERSION='2.4.*'
+        - php: 5.5
+          env: SYMFONY_VERSION='dev-master'
     allow_failures:
         - env: SYMFONY_VERSION=dev-master
 
 before_script:
     - composer self-update
-    - composer require symfony/twig-bundle:${SYMFONY_VERSION} --no-update
-    - composer require symfony/twig-bridge:${SYMFONY_VERSION} --no-update
-    - composer require symfony/framework-bundle:${SYMFONY_VERSION} --no-update
-    - composer require symfony/validator:${SYMFONY_VERSION} --dev --no-update
-    - composer require symfony/console:${SYMFONY_VERSION} --no-update
-    - composer require symfony/css-selector:${SYMFONY_VERSION} --dev --no-update
-    - composer require symfony/browser-kit:${SYMFONY_VERSION} --dev --no-update
-    - composer require symfony/yaml:${SYMFONY_VERSION} --dev --no-update
-    - composer require symfony/form:${SYMFONY_VERSION} --dev --no-update
-    - composer update
+    - sh -c 'if [ "$SYMFONY_VERSION" != "" ]; then composer require --no-update symfony/symfony=$SYMFONY_VERSION; fi;'
+    - composer install
 
 script: phpunit --coverage-text