Some kind of time delta for localized "business days"

[josefdlange]

It'd be interesting to see if we could subclass/contain timedelta into such a structure that we could pass in a count of business days, and if passed into an arithmetic function on Delorean, it'd have the end result be the appropriate number of business days away. This would be kind of naive as it wouldn't consider holidays, but nonetheless it seems it might be handy.

Worst case I write a function on my end that does the work externally, but I think it might be a neat feature in the library.