Added serialize method for transaction

Author: rg911

src/utility/TransactionMapping.ts

@@ -37,20 +37,4 @@ export class TransactionMapping {
     public static createFromPayload(dataBytes: string): Transaction {
         return CreateTransactionFromPayload(dataBytes);
     }
-
-    /**
-     * Serialize a transaction.
-     * @returns {string} Serialized transaction in binary.
-     */
-    public static serialize(): string {
-        throw new Error();
-    }
-
-    /**
-     * Create transaction class from Json.
-     * @returns {object} Serialized transaction in json object.
-     */
-    public static serializeJson(): object {
-        throw new Error();
-    }
 }