Intent to implement: State-specific holidays

[koterpillar]

In some countries each state decides their holidays more or less independently. Would you be interested in a PR that adds an optional state selector for those?

[hvianna]

I'm thinking of a different approach for this: user selects the country, we load all of that country's holidays and then let the user selectively enable/disable individual holidays via the UI.

[koterpillar]

If you look at #9, there are quite a few state-specific holidays (Australia) and it'd be tedious for the user to choose. If we know which holiday applies to which state, why not use that information?

[hvianna]

Ok, sure! Please note I'm merging the other in-development features to the dev branch, so use that as the base branch, please.

[koterpillar]

Thanks, I've based my branch on #10 so will open a PR as soon as that's merged.