Hipchat improvements

* Specs are now green
* Hipchat message now contains @ mentions
* Hipchat message now contain url for details. For this `gui_base_url` needs to be set in `workers.yml` to `https://dcc.infopark.de`
* Removed `short_identifier` of build to remove clutter.

The new hipchat message now looks like this:


> [Cloud Connector] scrival:test:integration failed - https://dcc.infopark.de/project/show_bucket/46093

or 

> [Cloud Connector] scrival:test:integration failed - https://dcc.infopark.de/project/show_bucket/46093 /cc @apepper

### Cruise

(almost) green dcc cruise: https://dcc.infopark.de/project/show_build/2751 . It's red, since it can not report to hipchat.