scrollToDate:animated: implementation.

This method allows the consumer to scroll to a given date month
instead of always starting in the firstDate month. Also allows to
programatically move the calendar view to a desidered date, either
animated or not.
Update TestApp to showcase scrollToDate:animated method.

The TestApp firstDate is one year in past, but the scroll is set to
today month after the views did layout.
Merge pull request #16 from drodriguez/scroll-to-date

Scroll to date