Deal with ids that contain slashes

The base64 encoding that is used for ids does not play nicely with the HTTP
route matching unless a regex is specified.
That's a good question that I don't know the answer to.

Another possible solution for this would be to use [base64url encoding](http://tools.ietf.org/html/rfc4648#section-5) for ids to prevent us from having to worry about this.