Call updateTimelines method when a new timeline is added
Add minDate and maxDate methods
Add a midRange method to calculate the halfway point between the min and max dates
Clean up the class code a little bit
Add some minimal comments
Add conversion methods between x coordinates and dates
Fix pan bug where items would jump when you start panning
Change Pan methods to work with dates instead of x coords
Merge pull request #47 from pk-nb/draw-it-all

Draw it all
Work on drawing events
Implement draw event function