PHP 5.3.3 on Travis doesn't like openssl

Fixes: https://travis-ci.org/sonata-project/SonataAdminBundle/jobs/66538085#L114

.travis.yml

@@ -21,7 +21,7 @@ env:
 matrix:
   fast_finish: true
   include:
-    - php: 5.3.3
+    - php: 5.3
       env: COMPOSER_FLAGS="--prefer-lowest"
     - php: 5.6
       env: SYMFONY_VERSION=2.3.*