Allow broadcast to compose without audio or video.

[Tr00d]

Add two fields "hasAudio" and "hasVideo" for broadcasts.

https://github.com/opentok/api-review/commit/f82528f7753eea2333e25339edfa87840d5b33fc

There's only one file to change:

• Current tests do not verify the request content (It.IsAny<Dictionary<string, object>>)
• No details on how to start broadcasts in readme