Merge into Base

[quinnj]

It's been long-discussed to merge this refactored code into Base, but my make-fu is quite poor and I'm not entirely sure how we want to go about it.
@StefanKarpinski, last we talked, it sounded like you had a good idea how to do the merge. I'm not sure if we would do a submodule a la libuv, with the code still residing in this repo (or JuliaLang/Dates.jl), or if we just want to haul all the code over. There's also the question of where it should live. Is base/dates/ good enough? Do we want to carve out a process for future non-core stdlib packages with something else?

[StefanKarpinski]

I think it should just be moved into the main Julia repo – or at least some of it should. Submodules are a constant pain and this is going to be fairly strongly integrated – some functions in Base ought to return date/time objects.

[quinnj]

Should I make a PR immediately, or should we code review what's here first?

[StefanKarpinski]

Go for the PR. Follow the Pkg model / various other things that have their own modules in Base.

[IainNZ]

Close?