Allow getting request path tail about warp

[seanmonstar]

I agree! What seems more useful, getting the raw path, or getting some Segments that is an iterator over remaining segments?

[lnicola]

I would need the raw path, but an iterator might be nicer in general. Any other opinions?

[seanmonstar]

Nothing prevents there being both warp::path::segments() and warp::path::tail()!

For the tail, it'd be nice if it could just return the &str of the path, but I don't think that can work, since the compiler can't prove that the future doesn't live longer than the request (maybe async will allow this?). So for now, it could return a newtype, struct Tail(http::uri::PathAndQuery, usize) that can be used to grab the &str.