Update comments to reflect new name for redirector

Also to reflect that we don't import mappings from redirector any more (and
haven't for a long time).
Rename some methods containing redirector

These were either no longer accurate or misleading - the hits import dealt with
hits from pre-transition logs and from post-transition logs - or no longer fit
the new name for the repo. Plus these names are shorter, which is nice.
Rename data/redirector to data/transition-config

If you already have this checked out, you can do one of two things:
* run `bundle exec rake notmodules:sync` to fetch it cleanly
* run `mv data/redirector data/transition-config`