ScatterGraph

-Created the ScatterGraph object
-Created the mouse handlers for the ScatterGraph object
-Created getOffset(e). It's just a utility function
-Made ScatterGraph's structure different, need to do the same to Pie
-Changed some things in Pie to make it look cleaner
-Split the data update function from the Draw function in ScatterGraph.
Makes it look cleaner and allows for less computing when checking during
the mouse events
-Added fit() to the super. It allows users to call .fit() only on
ScatterGraph objects