scatterpolargl display issue on IE11

[dmt0]

Here's an example that works in Chrome, but not in IE11.
https://bl.ocks.org/dmt0/6b47f10114efd50c3c6bba0c1a806045/95a201ad81b846da4dfc3ac2f767287b35ea26cf

From @alexcjohnson on slack:

[T]here’s a function isPath2DSupported but it throws if Path2D is undefined (as in IE11) https://github.com/dy/svg-path-sdf/blob/master/index.js#L83-L95 dy/svg-path-sdf#1 (also seems like we should be able to call that function just once and cache the result, right?)