Adds function which replays the animation when it is called, and zooming functionality

Replay animation:
If wayfinding is called with the 'animatePath' parameter, it hides the path on the screen, then redraws it like it did the first time. The path is cached so that it doesn't have to re-do the routing. A button could be added to let a user replay the last path if they didn't catch all of the directions.

Zooming:
If 'zoomToRoute' is set to true, the map will zoom in around the part of the route that is being drawn, with some space around the edges configurable by the 'zoomPadding' option. Might make it easier to grok large maps.