v2.0.0

• Add transition.easeVarying.
• Add transition[Symbol.iterator]; transitions are now iterable.
• Fix selection.transition to error if the named transition to inherit is not found. #45 #59
• Fix transition.end to resolve immediately if the selection is empty. #105
• Change d3-selection to peer dependency. #92
• Upgrade to d3-selection 2.

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-transition 1.x or use a transpiler.