Issue 39

There may still be some rough edges here. In particular, it feels like `CacheWriter.write(K, V)` needs to be split into insert and update, and return a value. Also, an attempt was made to whip compute/write functions for bulk CRUD methods into shape, to blaze the trail for fixing #110... not super convinced they are correct now though.
So you want to try and track the last argument set the function was invoked with, and "replay" the call with those only? I guess that makes sense but I wonder if scalability would be an issue, if one were to hook it up to tiered stores (e.g. clustered)... maybe this isn't the place to think about it though.