Use normal 5.3 instead of 5.3.3 for lowest tests

Prophecy doesn't supported \Traversable mocks in PHP 5.3.3

Author: wouterj

.travis.yml

@@ -24,7 +24,7 @@ matrix:
       env: SYMFONY_VERSION=2.4.*
     - php: 5.5
       env: SYMFONY_VERSION=2.6.*
-    - php: 5.3.3
+    - php: 5.3
       env: SYMFONY_VERSION=2.3.* COMPOSER_FLAGS="--prefer-lowest"
 
 before_install: