[TASK] Require green PHP 5.4 build on travis again

Change-Id: Ifd13543b1b3b337171214f70087bc7010b3c0898
Reviewed-on: http://review.typo3.org/16146
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn

.travis.yml

@@ -10,10 +10,6 @@ branches:
   only:
     - master
 
-matrix:
-  allow_failures:
-    - php: 5.4
-
 services:
   - memcached