Add a callback to the rewriteURI method
Fixes based on the PR comments
Merge pull request #57 from fhrbek/rewrite_uri_callback

WIP - Add a callback to the rewriteURI method
(TK-33) Add proxy redirect test

Add a proxy redirect test to the proxy test file.
(TK-33) Add redirect support to proxy

Add redirect support to the proxy by setting the HTTPClient
created by Jetty to follow redirects. Add tests for this
functionality.
(TK-33) Add `:follow-redirects` proxy option

Add a `:follow-redirects` proxy option, which allows the user to
specify whether the HttpClient created by a ProxyServlet follows
redirects.