Improved Travis Config and use new docker-based env

Author: wouterj

.travis.yml

@@ -7,32 +7,37 @@ php:
     - 5.6
     - hhvm
 
+sudo: false
+
+cache:
+    directories:
+        - $HOME/.composer/cache
+
 env:
-  - SYMFONY_VERSION=2.6.* PACKAGE_VERSION=high
+  - SYMFONY_VERSION=2.6.*
 
 matrix:
   include:
     - php: 5.3.3
-      env: SYMFONY_VERSION=2.3.* PACKAGE_VERSION=low
+      env: SYMFONY_VERSION=2.3.* COMPOSER_FLAGS="--prefer-lowest"
     - php: 5.6
-      env: SYMFONY_VERSION=2.3.* PACKAGE_VERSION=high
+      env: SYMFONY_VERSION=2.3.*
     - php: 5.6
-      env: SYMFONY_VERSION=2.5.* PACKAGE_VERSION=high
+      env: SYMFONY_VERSION=2.5.*
     - php: 5.6
-      env: SYMFONY_VERSION=2.7.* PACKAGE_VERSION=high
+      env: SYMFONY_VERSION=2.7.*
     - php: 5.6
-      env: SYMFONY_VERSION=3.0.*@dev PACKAGE_VERSION=high
+      env: SYMFONY_VERSION=3.0.*
   allow_failures:
     - php: 5.6
-      env: SYMFONY_VERSION=2.7.* PACKAGE_VERSION=high
+      env: SYMFONY_VERSION=2.7.*
     - php: 5.6
-      env: SYMFONY_VERSION=3.0.*@dev PACKAGE_VERSION=high
+      env: SYMFONY_VERSION=3.0.*
 
 before_script:
   - composer self-update
   - composer require symfony/symfony:${SYMFONY_VERSION} --no-update
-  - if [[ "$PACKAGE_VERSION" == "high" ]]; then composer update --prefer-source; fi
-  - if [[ "$PACKAGE_VERSION" == "low" ]]; then composer update --prefer-lowest --prefer-source; fi
+  - composer update --prefer-source $COMPOSER_FLAGS
 
 script: phpunit --coverage-text