fixing ExpirationDate #371

Author: abuzuhri

Source/FikaAmazonAPI.SampleCode/FeedsSample.cs

@@ -318,7 +318,8 @@ public void CartonContentsRequestFeed()
                         new CartonItem() {
                             QuantityInCase=12,
                         QuantityShipped=12,
-                        SKU="4051"
+                        SKU="4051",
+                        ExpirationDate=DateTime.Now,
                         }
                     }
                     }

Source/FikaAmazonAPI/ConstructFeed/Messages/CartonContentsRequest.cs

@@ -40,5 +40,11 @@ public class CartonItem
         public int QuantityShipped { get; set; }
         [XmlElement(ElementName = "QuantityInCase")]
         public int QuantityInCase { get; set; }
+        [XmlElement(ElementName = "ExpirationDate")]
+        public Nullable<DateTime> ExpirationDate { get; set; }
+
+        [XmlIgnore]
+        public bool ExpirationDateSpecified { get { return ExpirationDate != null; } }
+
     }
 }