Include the body of the request in the UnhandledHTTPRequestError when matching on the body

If either the current cassette or the default cassette options include the body as a matcher, show the body of the request in the UnhandledHTTPRequestError to help identify the unhandled request.
Only look to the current cassette's options when determining whether to show the request body in the UnhandledHTTPRequestError if there is a cassette.

If the current cassette is not matching on the body, the default matching option is irrelevant.
Merge pull request #360 from cgunther/unhandled-request-body-in-error

Include the body of the request in the UnhandledHTTPRequestError when matching on the body