With the new LRU cache store added in #535, I want to encourage individual processors to try to down their own local caching if they do anything super expensive. Shelling out to execjs is one of those expensive things. This is going to work best with processors that are pure functions, take the input, transform it and return a value. Processors reaching out to the FS are going to have to manage their own complex caching strategy.

The situation right now is bumping `version` and waiting 100x longer to recompile everything. The overall direction is to have smaller scoped caches and cache keys to bump.