[TASK] Start memcached on travis-ci build

Travis CI does not start memcached by default any more.
Add the memcached service to the travis.yaml

Change-Id: I27f4de6e1c0685632516b18c30858d61b793656e
Reviewed-on: http://review.typo3.org/15479
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel

.travis.yml

@@ -10,6 +10,9 @@ branches:
   only:
     - master
 
+services:
+  - memcache
+
 before_script:
 # Install build dependencies
   - git clone git://github.com/typo3-ci/TYPO3-Travis-Integration.git build-environment