Handle negative business days and hours

[xlts]

No description provided.

[bokmann]

Can you provide a business need / example of where negative business days/hours is used? I really appreciate the tests you've written to cover this; I just want to understand the business consideration before adding it to the gem.

[xlts]

@bokmann Thanks. I don't think anyone would use it deliberately like -3.business_days.before(date); this pull request basically addresses the unexpected behavior described in #119. However, in my project I do plenty of business time calculations and often find myself adding checks in the fashion of calculated_days > 0 ? calculated_days.after(date) : calculated_days.before(date), in such case this if statement would not be needed and everything would work, well, according to the principle of least astonishment when called on negative numbers.

[bokmann]

Thanks for the explanation. I'll be merging this and releasing next week when I teach an internal class on release management.