reduce browser bundle size

reduces browser bundle size by ~612k or ~92%.

src/util/requestUtils.ts

@@ -1,5 +1,3 @@
-import { createHmac } from 'crypto';
-
 export interface RestClientOptions {
   // override the max size of the request window (in ms)
   recv_window?: number;
@@ -23,12 +21,6 @@ export interface RestClientOptions {
 
 export type GenericAPIResponse = Promise<any>;
 
-export function signMessage(message: string, secret: string): string {
-  return createHmac('sha256', secret)
-    .update(message)
-    .digest('hex');
-};
-
 export function serializeParams(params: object = {}, strict_validation = false): string {
   return Object.keys(params)
     .sort()
@@ -75,4 +67,4 @@ export function isWsPong(response: any) {
     response.ret_msg === 'pong' &&
     response.success === true
   );
-}
+}