Forwards to local services regardless of path and REST method, and can proxy them rather than redirect

[dbraley]

Resolves Issue https://github.com/typicode/hotel/issues/350.

I have an interest in using hotel to manage not just UI servers, but also RESTful services as well. In order to do that effectively, we need to be able to accept multiple REST methods, not just GET, and be able to serve paths beyond just the root.

Unfortunately, most clients do not deal with redirects on non-GET methods particularly well (though the change #353 by @christianwerz made to switch the redirect to a 307 does help some clients). Because of that, I've also added the ability to specify a --forward-by-proxy option when doing an add which will tell the router to proxy the request directly, rather than returning a redirect.

[dbraley]

Oh, I should mention this branch is based on the nice work done by christianwerz here: https://github.com/typicode/hotel/pull/353