The current situation with unit tests has some shortcomings, this branch brings the following improvements:

• add a way to override the fedmsg configuration loading process, to avoid connecting to the prod database at the start of the testing phase.
• improve coverage by excluding the tests themselves from the report and generating the HTML report, which is much more useful (and fast to generate)
• split the huge test_fedora_hubs_api.py file into smaller files in a subdirectory
• improve the testing decorators in hubs.tests to handle more cases and be more versatile
• other more minor refactoring

Once again, there are many commits, .... you know the drill ;-)

The aim is to make it easier to run the tests, and to make them more independent from the production database / cache / fedmsg config.