#57 Fix defaultDate functionality

[peterox]

Fix for issue #57.

I don't believe that there is a need to set the date to null so the change should not effect any functionality.

[op16]

Sorry, but it has side effects: the Close and Clear actions keep the default date unchanged (the previous start of range).

[peterox]

I don't understand what you mean. Can you please better explain what is broken because of this change.

[op16]

1. comment out your customization of beforeShowDay() (not sure if this step is necessary, just to make sure you are seeing what I'm seeing)
2. select a range and press Apply
3. open the picker again and press Clear
4. open the picker again and notice the previous start of range looks different with your fix (because it is marked as current-day)