Add interactive querying of items

We select a bin with an expoentially-distributed pseudo-random number,
(so the items that have been misses the most get the most repetition),
then select an item within that bin with a uniformly distributed
random number. After querying the user, the item's count is adjusted
to the next higher/lower positive/negative number if the user's
response is correct/incorrect. And the item is moved into the new
bin based on its count.