Added /metadata and /metadata-server endpoints.
Added /metadata and /metadata-server endpoints.

To do so, refactored handle_download parsing code into common function get_package_info.

These endpoints return JSON of the relpath and checksums, unless "request.accept? 'text/plain'" is true. In that case, it returns plaintext of "url", "md5", and "sha256", each on new lines, with key and value seperated by tabs.

rhass/opscode-omnitruck,juliandunn/opscode-omnitruck,glennmatthews/opscode-omnitruck,glennmatthews/opscode-omnitruck,chef/opscode-omnitruck,chef/omnitruck,rhass/opscode-omnitruck,rhass/opscode-omnitruck,juliandunn/opscode-omnitruck,glennmatthews/opscode-omnitruck,chef/opscode-omnitruck,chef/omnitruck,juliandunn/opscode-omnitruck,chef/omnitruck,chef/opscode-omnitruck