Added content_type :binary, "application/octet-stream"

Updated request_response_spec test for new content_type

Updated CHANGELOG

Added tests for application/octet-stream and other untested content-types

Updated README for undocumented content-types. Flipped :binary and :txt order in content_types.rb

Removed atom, rss, and jsonapi content-types since they were never properly supported. Updated test for binary content-type.