Chad Scherrer

Ok, I have at least a start on this. I'll PR soon to see what you think.

Hmm, maybe `unique_id` should be the same as `name` for globals, and we only increment the counter for local variables?

Ok, I think I understand, but just to be sure... For two `LocalVar`s, are the `LocalVar.is_mutable`s the same (`===`) exactly when the `LocalVar.is_shared`s are the same?

That would make sense, but it's not such a big deal either way. I think I'd refactor it this way if you think you'll be extending it more, since that...

Ok, I've updated the PR. Also, what do you think of allowing another method passing an `id_function`? I've prototyped the idea here: https://github.com/cscherrer/JuliaVariables.jl/pull/1