fix Issue #223

my dates are getting picked right, but not saved right, due to formatting problems...

mymodel.showtime = '4/27/1980' sets showtime to nil.

switched it to '1980-04-27'

works for me, sorry about the sneaky commit with the gemspec... just merge this after you are ok with the gemspec changes, or i can rebase if needed... my example app is a rails 4.0 app, so i'm working off of another pending pull.