Uri methods

Well, it seems @tlunter and I have been stepping on each other today :)

Given the changes in #303, this would allow VCR to simply call `connection.request_uri(request_params)`.

I would rather create a single `Utils#to_uri` method, so you could call `@connection.to_uri` or `@request.to_uri`, but this would require passing a Request instance to the middlewares instead of a Hash. As I mentioned in #303, I'd like to move in that direction, but for now I think having these two methods is the best option.