Feature/ajax improvements

Fixed a bunch of bugs, and added enhancements to Ajax.

- Support HTTP Basic Auth
- Don't emulate standard HTTP verbs for REST unless told to do so
- Support the 'X-Http-Method-Override' header in addition to _method, which is rails-specific and broken in many versions of Rails
- Fixed inability to set Content-type header on methods other than POST with a PostBody
- Allow setting postBody on PUT requests

Also cleaned up some tests