Refactored code to take advantage of the "use strict" methods (prevent variables from falling into the global namespace)
Made line drawing a bit faster and more robust using new data structure. Fixed selection problem in clicking arrows.
Update arrows now occurs again on select_tr, because it doesn't take all that much processing time and makes code much easier.
  Added line to make certain svg area stays in place.
Some positioning improvements. #container now expands and collapses with top menu.