made HR::Link#post (et al) work without performing an implicit get

Bugfix: calling `post` on a `HR::Link` would first perform a `get` on the link's resource.  This is bad behavior, but would only raise errors when the `get` would fail, such as when the GET method is not allowed on the URL.

This PR fixes this bug, so that `post/put/patch/delete` perform only the desired action, with no pre-`get`.