Hoverlabels are too slow with more than a few layers #55
Description
Right now if you just plot 2 teams and the ball hoverlabels work fine — they're responsive and don't crash the chrome tabs. But if you try to plot players from a bunch of teams at once, maybe to look at positions on the field at the time of certain important events, then things start to chug. This happens when using the Pick or the Circle glyphs. This is probably happening because each team is coded up as its own separate layer, and bokeh is not optimized to deal with that.
The fix is almost certainly to change the plotting functions to work on multiple teams/balls in one loop, which is going to be non-trivial.