Release 1.7.4

* Auto-link SHA1s and Gerrit change IDs
* Enable logging to Twitter via Twitter API v1.1
* Release for precise.
* Add Recommends: python-twitter.
* Bump Build-Depends debhelper & compat to 9.

Change-Id: I63c2d9763bbd2abfe520fe867d551eb041d9eee3