JSON.{dump,generate} offered by the JSON gem is not compatiable with
Rails at the moment and can cause a lot of subtle bugs when passed
certain data structures. This changed all direct usage of the JSON gem
in internal Rails code to always go through AS::JSON.{decode,encode}.
We also shouldn't be implementing `to_json` most of the time, and
these occurances are replaced with an equivilent `as_json`
implementation to avoid problems down the road.
See [1] for all the juicy details.
[1]: intridea/multi_json#138 (comment)
Move the Journey code underneath the ActionDispatch namespace so
that we don't pollute the global namespace with names that may
be used for models.
Fixesrails/journey#49.