If a nodified method does not return a Promise, it will throw an error, like this:
```
Error in event handler for (unknown): Error: The function setSelectedAccount did not return a Promise, but was nodeified.
```
Mostly Fixes#893
A couple methods cache callbacks, and will require a larger refactor to fully denodeify.
Specifically, our methods involving web3 requests to sign a tx, sign a message, and approve or cancel either of those.
I think we should postpone those until the TxManager refactor, since it will likely handle this response caching itself.
