restsharp/RestSharp — pull request #488 by esthereisner (2013-12-22 21:25:57+00:00)
Title: Excluded all non "oauth_" parameters from the signature for multipart re...

...quests.

Discovered issue when attempting to post to Twitter with media attached.
Per Twitter docs (https://dev.twitter.com/docs/uploading-media) oauth
should be handled differently in this scenario.