Russell, would you mind renaming `random_int` to be `uniform_int` instead?  And make the same change to `counters.config`?  That would match the generator of the almost-same-name found in `basho_bench_keygen.erl`.

Come to think of it, for symmetry's sake, would you mind also adding the `{uniform_int, StartKey, NumKeys}` flavor to the valgen also?