Allow OPTIONS requests for formats responded to inside scopes

Because #generate_options_routes! is called after all scopes are
unwound, we have to go back and grab the relevant formats when
defining the matching OPTIONS routes.

Signed-off-by: Evan Owen <kainosnoema@gmail.com>
Merge pull request #30 from stephencelis/fix-options-formats

Allow OPTIONS requests for formats responded to inside scopes