Bump version to 2.1.1
.NET Client: Dispatch failed hub invocation callbacks on reconnecting
- #3101
Respond to JSONP send requests with the correct MIME type

#3110
Rewrite ProcessStartRequests to not use async/await to avoid deadlocks

- Deadlocks would occur in the old async/await code if someone attached
  to the PreSendRequestHeaders event.
Attach to the PreSendRequestHeaders event for only one test