The response from RestMan on a raw request looks like a string, but is
actually one of these.  99% of the time you're making a rest call all you
care about is the body, but on the occasion you want to fetch the
headers you can:

  RestMan.get('http://example.com').headers[:content_type]

In addition, if you do not use the response as a string, you can access
a Tempfile object at res.file, which contains the path to the raw
downloaded request body.