What does this implement/fix? Explain your changes.

Drop implicit conversion of List<> and IEnumerable.

Does this close any currently open issues?

Heaps, I'll list them later

Any other comments?

Breaks the interface, so we'll have to announce this loudly and raise the minor version number.

Checklist

Check all those that are applicable and complete.

• Make sure to include one or more tests for your change
• If an enhancement PR, please create docs and at best an example
• Add yourself to AUTHORS
• Updated the CHANGELOG