release notes 2.0

[mesqueeb]

Hi! I can't find the release notes for v2.0. Also couldn't find a changelog.md

What are the breaking changes?

[papandreou]

The breaking change was:

• drop support for node <6 (#419) (Timofey Kachalov)

And this one also landed:

• add support for optional chaining (#412) (Timofey Kachalov)