Fixes #19 - Add support for source-map generation

The generated sourcemap is not very helpful as of yet, but I'm working on that. I think this is probably a better solution than the alternative method attempted earlier :)

The `astral-angular-annotate` module will need to be updated to update the locations of items, I think. But it's sort of difficult to work out how it's intended to actually work.

I don't know how this will work with source-map chaining as of yet, that is a more involved test, I'll do more of that once it's a bit further along I suppose.