Added Deck and Card classes.

Created initial Deck class and Card class.

Cards can be created and added to a deck.
Cards can be drawn from the deck.
A deck can have its cards shuffled.

Cards drawn from one deck will not be automatically removed until they are placed into another deck, or are explicitly removed from the deck after being drawn.

If a card is explicitly removed from a deck, it will still hold the reference of the deck it belonged to until it is placed into another deck. This allows for the card to be re-introduced back into its deck.