Added adapter for Jasmine 2

Here's an adapter for Jasmine 2. Jasmine 2 is still in RC phase, but we'll see.

Note that this is only the adapter, not the runner. I don't use it myself; let me know if it takes you one minute to do it or would like me to go through it (no problem!).

Let me know what you think, and I'll be happy to work with you on this PR.