Update travis-ci config

Author: willdurand

.travis.yml

@@ -1,19 +1,25 @@
 language: php
 
 php:
-  - 5.3
-  - 5.4
-  - 5.5
+    - 5.3
+    - 5.4
+    - 5.5
 
 env:
-  - SYMFONY_VERSION=2.0.7
-  - SYMFONY_VERSION=2.1.*
-  - SYMFONY_VERSION=2.2.*
-  - SYMFONY_VERSION=dev-master
+    - SYMFONY_VERSION=2.0.7
+    - SYMFONY_VERSION=2.1.*
+    - SYMFONY_VERSION=2.2.*
+    - SYMFONY_VERSION=2.3.*
+    - SYMFONY_VERSION=dev-master
+
+matrix:
+    allow_failures:
+        - env: SYMFONY_VERSION=dev-master
+
 
 before_script:
-  - curl -s http://getcomposer.org/installer | php
-  - php composer.phar require symfony/framework-bundle:${SYMFONY_VERSION} --no-update
-  - php composer.phar update
+    - curl -s http://getcomposer.org/installer | php
+    - php composer.phar require symfony/framework-bundle:${SYMFONY_VERSION} --no-update
+    - php composer.phar update
 
 script: phpunit --coverage-text