Upsert with compound primary key

`upsert` does not work as I would expect with a compound primary key. The workaround I use is to use `insert` with `replace=True` to accomplish what I think `upsert` should do.

This is a minimal repro of the issue I ran into when developing on the solveit app: https://gist.github.com/Isaac-Flath/cc9b3c5d28219725235b00241ce4082a

FYI @pydanny @audreyfeldroy @jph00