PEP8 and other cleanups.

* Remove unused variables and imports.
* Remove superfluous spaces.
* Some PEP8 formatting.
Use correct app name in tests.
Isolate tests more by using global_settings middleware.
Remove db_table on model so default table name is used.

The tb_table name clashes with the django redirects app db_table name
which means both apps can't be used at the same time. Having both apps
active is useful when you want to migrate from one app to anther.
Merge pull request #2 from benkonrath/minor-bug-fixes

Minor bug fixes