remove request/response info from HTTPStatusError message
remove request/response info from HTTPStatusError message

This prevents Excon from inadvertently displaying sensitive information,
and producing large error messages when request[:body] is a String.

All HTTPStatusError exceptions provide access to the request and
response, and may be rescued and inspected for debugging purposes.

Closes #219

mahemoff/excon,ilackarms/excon,hammerdr/excon,wadetandy/excon,TheNeatCompany/excon,liftforward/excon,excon/excon,cloudfoundry-incubator/excon