[TASK] Use travis only for master branch

Change-Id: I2b8e67af2a8baaa7a9785751d80bb7c7344b27e3
Reviewed-on: https://review.typo3.org/28959
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer
[TASK] Followup cleanup for sys_category usage

Change-Id: I52cd850663a3d64bee6a61e7ca8b867f44edad49
Reviewed-on: https://review.typo3.org/28958
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer