v0.2.5 Fixed the additions of weekdays on dates that span weekends.

i.e new Date(2013, 11, 19, 0, 0, 0) + 3 weekdays should be tuesday not Sunday


- [ ] @achura 
- [ ] @andymoon 
- [ ] @aheuermann 
- [ ] @jvanwinkle 
- [ ] @jkc