Merge pull request #173 from ctreatma/feature/fix_json_dependencies

Use Rails format routing to match the RubyGems API
Revert "Use Rails format routing to match the RubyGems API"

This reverts commit 566ed9488b68c2c0bddf2b6c8386acf7ff540569.
Use Rails format routing to match the RubyGems API

A previous version of this commit broke bundler because
the controller was responding to JSON at unexpected times.
Hitting the dependencies endpoint in a browser returned
marshalled Ruby objects, but hitting that endpoint with
curl returned JSON.

To fix that issue, this commit reverses the order of
format checks so that the dependencies endpoint responds
with marshalled Ruby objects when the response format is
ambiguous.