Handle text, text/plain, and auto dataTypes.
Add request res callback param and various fixes.

- Add a 'res' param to the request callback to provide callers with the
  http.ClientResponse if needed. For URLs this can be used to check
  status codes, headers, etc.
- Various fixes and jshint and strict cleanups.
- Don't parse content if Content-Length is 0.
- Check lowercase types.
- Make --base a common option.
- Only have long-form for rare options.
- Add some format aliases.