Pass options through to Rails' routing DSL

It would be nice to use the same options that Rails allows for, say,
namespacing an API. I use a subdomain for my API, which makes `/api` in
my path a redundancy. Instead of throwing away options that aren't
`:vendor_string`, pass them through to Rails.

Signed-off-by: David Celis <me@davidcel.is>
Merge pull request #1 from davidcelis/master

Pass options through to Rails' routing DSL