Update URLs
Remove PyPI classifiers b/c not needed on PyPI anymore. Hoping this fixes mysterious travis error, too.
Force setuptools==7.0 to fix a mysterious issue the human race is
incapable of fully understanding.
+ Tag.slug index, oops!

Turns out `unique_together` only creates a multi-value index, not an
index on each attribute (like I'd incorrectly assumed)
Tag autocomplete should use slug (index)
Replace inefficient, slow link count query.

The query before wasn't actually doing anything different from a simple
count, and was taking ~14 seconds to run in some cases!  Replaced with
a simple, faster count.
Increase link cache time to 15 minutes
Index history_date on versioned models.

According to the slow query log, this was slowing down some history
queries.
Some more indexes on region models.