message: expect a Blockstack API Url from the auth response; set it globally once parsed
diff: @@ -157,13 +157,14 @@ export function handlePendingSignIn(nameLookupURL: string = '',
  if (!nameLookupURL) {
  // given in the authResponseToken?
  const tokenPayload = decodeToken(authResponseToken).payload
  - if (!!tokenPayload.nameLookupUrl) {
  - nameLookupURL = tokenPayload.nameLookupUrl
  - } else {
  + if (!!tokenPayload.blockstackAPIUrl) {
  + // override globally
  + config.network.blockstackAPIUrl = tokenPayload.blockstackAPIUrl
  + }
  +
  // default
  nameLookupURL = `${config.network.blockstackAPIUrl}/v1/names/`
  }
  - }
  return verifyAuthResponse(authResponseToken, nameLookupURL)
  .then(isValid => {
  if (!isValid) {
  