Find Clean Solution to Diffing Hierarchies

[bplunkett-stripe]

Diffing hierarchies like indexes is pretty gross right now. If the parent index is re-created, we need to push that re-create down to the child indexes. There's no good way of doing this, so we're forced to use a hackaround where when diffing the child indexes we:

1. Use the old and new schema map to fetch the old and new parent
2. Diff the old and new parent to figure out if we need to re-create them

[bplunkett-stripe]

Closing in favor of #131