Remove d3-module keyword.
Remove d3-module keyword.

I’d like the d3-module keyword to be used only for modules that use the D3 4.0 module pattern as documented in [Let’s Make a (D3) Plugin](https://bost.ocks.org/mike/d3-plugin/). This library is targeted at D3 3.x because it depends on the global `d3` and D3 3.x API’s such as d3.scale.category10. Would you mind removing the d3-module keyword, at least until this library is updated to support D3 4+?
uwgraphics/d3-twodim