Fix for CSHARP-374

Author: ALyman

Bson/ObjectModel/BsonDocument.cs

@@ -1200,6 +1200,9 @@ private object ToDictionaryHelper(BsonValue value)
                 case BsonType.Document:
                     return value.AsBsonDocument.ToDictionary();
 
+                case BsonType.DateTime:
+                    return value.AsDateTime;
+
                 default:
                     return value.RawValue;
             }
@@ -1217,6 +1220,9 @@ private object ToHashtableHelper(BsonValue value)
                 case BsonType.Document:
                     return value.AsBsonDocument.ToHashtable();
 
+                case BsonType.DateTime:
+                    return value.AsDateTime;
+
                 default:
                     return value.RawValue;
             }