Expose the request object for each request.

For my context, I'd log to log all requests made by my application, their status codes, and other information about the request. At the same time, I'd like to this library for contacting Cryptsy as it does a lot of the hard work for me.

This pull request exposes the request objects via the `api`, `getRequest` and `postRequest` methods so the requests themselves can be logged and tracked, say, by listening to the request object's "complete" event.