Created Hand Type

Created a Hand type that can also calculate the sum of the cards in the
hand. Also wrote a display for it so that we can just print hands out.

tests/hand_tests.rs

@@ -0,0 +1,40 @@
+use blackjack::Card;
+use blackjack::Hand;
+
+const ACE_HEARTS: Card = Card { suit: 0, value: 0 };
+const ACE_SPADES: Card = Card { suit: 3, value: 0 };
+const KING_HEARTS: Card = Card { suit: 0, value: 12 };
+const KING_SPADES: Card = Card { suit: 3, value: 12 };
+
+#[test]
+fn test_double_ace() {
+    let mut hand = Hand::new(false);
+    hand.get_new_card(ACE_HEARTS);
+    hand.get_new_card(ACE_SPADES);
+
+    assert_eq!(12, hand.sum());
+}
+
+#[test]
+fn double_ace_double_face() {
+    let mut hand = Hand::new(false);
+    hand.get_new_card(ACE_HEARTS);
+    hand.get_new_card(ACE_SPADES);
+    hand.get_new_card(KING_HEARTS);
+    hand.get_new_card(KING_SPADES);
+
+    assert_eq!(22, hand.sum());
+}
+
+#[test]
+fn show_all_is_dealer() {
+    let mut hand = Hand::new(true);
+    hand.get_new_card(ACE_HEARTS);
+    hand.get_new_card(KING_SPADES);
+
+    assert_eq!(10, hand.sum());
+
+    hand.set_show_all(true);
+
+    assert_eq!(21, hand.sum());
+}