Wiping state does not appear to work

[elijahbenizzy]

When calling:

state.wipe(keep=...)

as part of an action, it doesn't apply the difference. This is because we use a merge operation on a subset of the state, which is added back in. Thus if its missing it doesn't matter, it just takes the old value. Two options:

1. (short-term) Check the missing keys and delete them from the final state (this is a bit of a hack but it should work). We have to do this by diffing the state before/after update and remembering the missing ones.
2. (medium/long-term) Instead of diffing the state at each step, we should just apply deltas. Then we do a commit operation afterwards, which gather all of them. The fork/merge op will just gather the deltas, then we apply them to the final state in the order we got them in.

(1) will be good for v0

[elijahbenizzy]

This is fixed: #29