Support resource groupings for prefixed APIs

[aew]

The fact that an API has a prefix (e.g., /api) should not affect the
way resources are grouped for documentation purposes. This patch
updates the hardcoded single level of resource grouping to ignore the
prefix (which available as part of the route object).

[aew]

Note - this is an alternative implementation to https://github.com/tim-vandecasteele/grape-swagger/pull/52

[tim-vandecasteele]

Thanks, has been merged.

[kranzky]

To get this to work properly, I needed to change parse_path to take the prefix into account as well, as follows:

            def parse_path(path, version)
              # adapt format to swagger format
              path = path.split(route.route_prefix).last
              parsed_path = path.gsub '(.:format)', ( @@hide_format ? '' : '.{format}')
              # This is attempting to emulate the behavior of
              # Rack::Mount::Strexp. We cannot use Strexp directly because
              # all it does is generate regular expressions for parsing URLs.
              # TODO: Implement a Racc tokenizer to properly generate the
              # parsed path.
              parsed_path = parsed_path.gsub(/:([a-zA-Z_]\w*)/, '{\1}')
              # add the version
              version ? parsed_path.gsub('{version}', version) : parsed_path
            end