Added support for ddescribe and iit for Jasmine2.0 branch.

I've made an attempt to add `ddescribe` and `iit` support to the Jasmine 2.0 branch. The code has been pilfered from Jasmine Karma, like #185.

This isn't fully complete, as I can't get `iit` working. Whenever I modify a spec to use `iit`, I get the following:

```
Started 1 tests, but only had 0 complete
0 Tests, 0 Failures, 0 Skipped
 ```

So it seems to understand that the spec is to be run in isolation but for some reason it doesn't complete it. Can anybody shed some light on why this might be?