Store the require cache a little later.

I mentioned in #16 that I had issues with the retiring of the `require` cache. Inspecting the cache, then asynchronously restoring it to a previous state appears to be dangerous (though it doesn't feel that it should be).

Saving the cache values a little later resolved my issue (maybe not perfectly), but I suspect that it will only resolve the issue the majority of the time, and that this won't fix 100% of issues that could arise because of this.