v2.0.1

• Add interpolateZoom.rho. (#25)
• Allow d3.piecewise to default to using d3.interpolate. #90
• Change d3.interpolateTransformCss to use DOMMatrix and require absolute units. #83

This release adopts ES2015 language features such as for-of and drops support for older browsers, including IE. If you need to support pre-ES2015 environments, you should stick with d3-interpolate 1.x or use a transpiler.