Use dumped key values in delete statements

The key values in delete statements were being passed as-is to the adapter, resulting in invalid queries for cases like enums. This PR now converts the values using the property's `dump`, first.

Also, this branch is based off of the basic collections support branch (PR #5), as the dev dependencies referenced by master no longer work.

@dkubb Let me know if you'd like me to merge these PR's myself. I just wanted to run changes by you first, but I can merge to master myself in the future, if you'd prefer.