Add ability to refresh leg positions during tour

Let caller use bus.refreshLegPositions()  to call leg.refreshPosition()
on each leg in the tour to refresh its position relative to any data
element.  This can then be used by caller (eg setup as window.resize event handler when the tourbus departs and remove it when tourbus stops) to handle browser resizing to ensure leg positions are always correct.

Can use http://stackoverflow.com/questions/2854407/javascript-jquery-window-resize-how-to-fire-after-the-resize-is-completed technique in caller to avoid multiple calls to refreshLegPositions during a window resize drag.