Updated for jruby and ruby 2.0 support

I have been using a personal fork of this project for about 4 months at work.  This fork is based of of lxcid/ntlm-http I added a few more fixes so that it works in ruby-2.0.0-p0. I also updated the Rakefile so that the tests can actually run now.  

All tests are passing and I have tested it on jruby-1.7.2, jruby-1.7.3, ruby-1.9.3 and ruby-2.0.0-p0.