Update README.md
Adding some changes made by Taikero.
Allow cards to be forced

Allows cards to be forced in deck combinations, reducing the number of
permutations the sim will calculate. Also helps to rigorously test
specific deck combinations (allows all cards to be forced). Randomly
shuffles deck no matter if a card has been forced or not. Also only
calculates the number of cards allowed in the deck once instead of for
each deck permutation (small optimization).