Fixed NodeCenter function, and CustomDraw

Minor changes to the getNodeCenter function so it returns a Node object
instead of void and places the new nodes more nicely (might not need the
getNodeCenter function). Made changes in the CustomDraw function so it
will draw any existing edges, and uses the returned node from
getNodeCenter to draw the edge.
Merge pull request #1 from ASesz/KurtWorking

Fixed NodeCenter function, and CustomDraw