Implement date library using elixir 1.8s core functionality

[LostKobrakai]

As the title says. I'm just not sure what would be the best way to put tzdata into the deps, as really it's probably not even an optional dependency. It would just need to be available for :dev and :test.

[maennchen]

@LostKobrakai Thanks a lot for your PR. If you don't mind I would keep this PR open until tzdata is stable and then immediately merge & create a new release.

Why would it only need to be available for dev and test? This should work just as well in prod.

[LostKobrakai]

By now tzdata is the only actual implementation for an elixir timezone database, but the code I added would work with any implementation, so there's no need for quantum to require any tzdata version. It would rather just happen to be the implementation used in dev/test.

[coveralls]

Pull Request Test Coverage Report for Build 851

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 91.572%

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Totals
Change from base Build 850:	0.0%
Covered Lines:	402
Relevant Lines:	439

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💛 - Coveralls

[njwest]

Looks like tzdata has moved from rc to official 1.0.0 release as of April 24 @maennchen

[LostKobrakai]

This is still blocked because timex does not yet allow for tzdata 1.0: bitwalker/timex#530

[maennchen]

I'll try to work towards version 3. Since elixir offers all capabilities by itself, timex and calendar will no longer be needed. Therefore I'm going to merge this PR and remove all time libraries instead.