Can’t fetch URLs that don’t have .shp/.dbf extensions.

[mbostock]

Testing for .shp or .dbf at the end isn’t a good test for URLs. For example, it means you can’t pass a URL to an Observable FileAttachment (because those never have the .shp extension, and adding the .shp extension breaks the URL).

I think we should probably get rid of this magic. It might be okay to replace .shp with .dbf if the dbf argument is undefined, but otherwise I think we should leave the URLs as-is.

[polkerty]

Second this motion

[chadRoberge]

Not that it needs a third but....Third this motion.