DiceSet: includes knowledge of scoring dice

Functional representations of scoring and nonscoring dice functionality
in a functional DiceSet.  Plan is to include, eventually, entire game
history via pointers to previous activities.
Has scoring dice executed.
Greed::DiceSet reroll creates accurate DiceSet

This will create a new DiceSet that keeps the scoring items of the
current DiceSet, or a fresh DiceSet if it's full.
Accumulated score for a set of rolls.
Turns now work properly

Dicesets are easy, but maintaining immutability in turns means that I'll
have to be creating new turns on the regular, because they refer to a
DiceSet.

I want to do this to be able to maintain state as I go.  Eventually
turns will refer to a list of Turns, grouped into a list of Players
owned by a game.
Player and Game concepts added in.
Attempts to make the rolling safer.

Very fucking close.
Rolls now happen safely at the game level.
Merge pull request #1 from paulsalcido/extra-credit

Extra Credit: The main Greed::Game can do rolls forever.  There is some pretty stuff to add in, but the main part works without exception when just doing rolls over multiple runs.