added implementation to hand method stubs

src/main/java/io/zipcoder/casino/Hand.java

@@ -4,19 +4,24 @@ import java.util.List;
 
 public class Hand {
     private List<Card> list;
-    public void add(Card card) {
 
+    public void add(Card card) {
+        list.add(card);
     }
 
     public void remove(Card card) {
-
+        list.remove(card);
     }
 
     public Integer size() {
-        return null;
+        return list.size();
     }
 
     public Integer getValue() {
-        return null;
+        int sum = 0;
+        for(Card c : list) {
+            sum += c.getRank().getPrimaryValue();
+        }
+        return sum;
     }
 }