Remove any existing handlers for click on .day_holder a so that the hand...

...ler doesnt execute multiple times

Currently, this handler gets executed once for each time the user has selected "Weekly" from the recurring select dropdown because that's when this init method is run. Since the handler toggles selection of the clicked element, whenever the "Weekly" option is chosen an even number of times, the SMTWTF chooser becomes unusable (it toggles twice, four times, six times, etc which looks like a no-op to the user). We could restructure the application such that this init method only happens the first time "Weekly" is selected, but this simple fix squashes the bug.