Allow intercepting redirection responses

[deontologician]

Currently, redirection is automatic. It's sometimes useful to be able to examine the intermediate response.

Per the conversation in #26, I think it should be solved like this:

1. Create a new subclass of OrphanHALNavigator for redirections. It will have one additional method redirect that returns the fully functional HALNavigator that is usually produced by the redirection (except that it will also fetch the resource to avoid turning this into a 3 step process)
2. Add a flag keyword arg to POST/PUT/PATCH/DELETE operations similar to the request library's allow_redirects flag. Instead of performing the redirect automatically, it will produce one of these RedirectionOrphans

[deontologician]

Moving this out of the 1.0 release since it's backwards compatible. I have a start of this on josh/29