After an extended hiatus, rack-contrib maintenance is back on track.  This
is a tidy-up release, merging things that have sat around for far too long.

* `git-version-bump` has now been moved to being a development dependency,
  thanks to Tobias Haagen Michaelsen.

* `Rack::AcceptLocale` can be restricted to a set of enforced locales, thanks
  to Paco Guzman.

* `Rack::NotFound`'s `path` argument is now optional, thanks to Ed Morley.

* `Rack::BounceFavicon` now has a description and tests, thanks to Steven
  Wilkin.

* The automated Travis CI suite now tests all supported Ruby versions up to
  2.4, which necessitated a few small changes.