URL-safe Base64 for use in routes and params

Two questions:
1) I used `Base64.urlsafe_encode64` instead because that seemed to make sense, that ok?
2) Should it locate with a base64 encoded signed gid? If so, I can add another commit for that.
Ok, I looked at http://en.wikipedia.org/wiki/Base64 and it seemed ok since these ending equals signs are always padding to make blocks of 4 chars. I'll look at other solutions.