Tests don't pass. For some reason I have yet to understand, model
`Unrelated` (from core.models) is also managed by BungiesearchManager.
Fixes #37. Bungiesearch still connect to all models, but won't do
anything if the model isn't managed by BungiesearchManager. There
probably are better solutions than connecting to all models, but this is
the one Haystack uses too.
This is quite a major bug correction, so let's bump the version number.
Merge pull request #38 from Sparrho/issue-37

Fixes issue 37