strawman for ntlm support using rubyntlm gem

I have been trying to get [Savon](http://savonrb.com/) to work with ntlm connections, but I couldn't get it working with the ntlm experimental branch -- so here's a version (including unit and integration tests) using the newer rubyntlm gem.

here's the [writeup](https://github.com/coldnebo/httpi/wiki)