v4.0.0

This release causes remote transformers to be invoked even on deleted records, and thereby allows you to write a remote transformer that mutates record IDs (#510). It is a backwards-incompatible change because now a remote transformer must handle deleted records, which are missing all the normal fields you would expect from your records.

There are also some fixes to documentation errors (#515, #514) and updates of dependencies (#508, #512, #509, #502).