add OpenTok 2.2 to libraries

Description: "OpenTok: the leading cloud platform for adding live video, voice & messaging to your websites and mobile apps."

URL: https://tokbox.com/opentok/

I'm a developer evangelist at TokBox and I use JSBin in many of the demos I present as well as use it to help debug our users' issues. It would be wonderful to see the library available in the dropdown instead of manually copying and pasting it each time, and I'm sure our users would agree.