Revert "Failing spec for missing resource response on non-existent route."

This reverts commit 458f8bf7c2cb02dbed0b8e1de727542c78ff6149.
Revert "render a 404 from within the FSM."

This reverts commit 0c9ae2220957df20d47d71d52f1e8c8b1b102e3e.
quickfix for reel tests.

i think http gem v0.6.0 replaced HTTP::Header with HTTP::Headers but
reel/response.rb uses the older version from v0.5.0 HTTP::Header, so
we explicitly depend on http ~> 0.5.0 in the gemfile until fixed.
Merge pull request #157 from seancribbs/undo-notfoundresource

revert NotFoundResource.