Move Date monkey patching out of the main lib about holidays

[aripollak]

I would like this! Would a PR to do this be accepted? Obviously this would be a breaking change so the major version number would have to be incremented to adhere to semantic versioning.

Somewhat relatedly, is there any reason that holidays.rb ends up includeing Holidays inside Date? It doesn't look like that should have any useful effect.

[ppeble]

@aripollak Of course! I don't mind a major bump, it would be a nice addition.

To your question, I don't think you'll get an answer on why it was done that way. It was a long time ago. If it works without it then I think we're good to go.

[ppeble]

FYI for anyone working on this, I am going to roll this update into my refactor branch. Should have something up today.

[ppeble]

And it's done. I'm going to leave this issue open until we actually merge in the overall refactor just so I don't lose track of it.

Feedback welcome: https://github.com/ptrimble/holidays/blob/refactor/lib/holidays/core_extensions/date.rb

You can check out the updated README on my branch as well for usage.

[ppeble]

This has been merged.