title: Jquery increment yyyy-mm-dd date
body: <p>Mates, I'm trying to make a hostel booking reservation calendar on a Backbone application.
  I need to make week intervals to make the calendar, but the thing is that, having a YYYY-MM-DD date, i don't know how to increment day by day, knowing how many days has each month.</p>
  
  <p>Anyone has an idea?</p>
  
  <p>Thanks a lot!</p>