message: accept the name lookup URL from the authResponse token, so the Browser (or whatever is handling the sign-in) can pass in the name lookup URL being used.  Also, do not use a hard-coded string constant; use the blockstackAPIUrl from blockstack.config.network.
diff: @@ -19,6 +19,8 @@ import { extractProfile } from '../profiles'
  import { Logger } from '../logger'
  +import { network } from '../network'
  +
  const DEFAULT_PROFILE = {
  '@type': 'Person',
  '@context': 'http://schema.org'
  @@ -149,9 +151,19 @@ export function isSignInPending() {
  * @return {Promise} that resolves to the user data object if successful and rejects
  * if handling the sign in request fails or there was no pending sign in request.
  */
  -export function handlePendingSignIn(nameLookupURL: string = 'https://core.blockstack.org/v1/names/',
  +export function handlePendingSignIn(nameLookupURL: string = '',
  authResponseToken: string = getAuthResponseToken(),
  transitKey: string = getTransitKey()) {
  + if (!nameLookupURL) {
  + // given in the authResponseToken?
  + const tokenPayload = decodeToken(authResponseToken).payload
  + if (!!tokenPayload.nameLookupUrl) {
  + nameLookupURL = tokenPayload.nameLookupUrl
  + } else {
  + // default
  + nameLookupURL = `${network.blockstackAPIUrl}/v1/names/`
  + }
  + }
  return verifyAuthResponse(authResponseToken, nameLookupURL)
  .then(isValid => {
  if (!isValid) {
  