* Let's get rid of the two functions above and instead use `set_index_flag/2` directly.

* Add a doc explaining that the index flag indicates whether or not the KV object's value should be indexed.  If `false` only the minimal amount of information about the object is indexed so that Yokozuna knows about it and AAE can function correctly.  If `true` then the object's value will be indexed as well.

* Add spec.