I hate time zones. So much. Just use UTC.

* Created the _GenericProperty class to tidy up Generic Properties.
* Figured out how to properly manage time zones (added a timezone field
  to Change protobufs in order to handle time zones)
* Relevant tests
* Created a test_changelog file, which contains a SourcePackage with a
  changelog structure as should be generated from test_changelog. It
  also contains a list of strings that corresponds to the lines in the
  fixed changelog (created test_changelog_fixed).