Viewing elevation/time

[pcurrier]

Just an FYI -- I needed a bit of extra functionality, specifically the ability to see the time/elevation at any point along the track. So for each polyline I added an onclick handler that opens an info window, centered on the nearest track point neighbor to the click location, that shows the time/elevation for that point. The nearest neighbor is found by storing all points in a quadtree (https://github.com/d3/d3-quadtree).

If you'd like to include these changes, I can submit a pull request for you. If not, that's fine too.

https://github.com/pcurrier/gpxviewer