Update guard compat

With this guard-jasmine should be "protected" from upcoming major Guard refactoring.

- uses Guard::Compat API (except for Jasmine Server)
- tested on guard-jasmine-rails-test
- development: same changes as guard-coffeescript 2.0 will have (once I get gem access)

Let me know if you have any issues/requests with this PR or with Guard or Guard::Compat.

I'm pretty much done with Guard::Compat and updating all the plugins, so if there's anything useful missing from the Compat API, let me know (open an issue in Guard::Compat).