message: have client constanst call be unauthenticated
  Reviewers: arik
  Subscribers: ben
diff: @@ -1665,9 +1665,10 @@ BitGo.prototype.fetchConstants = function(params, callback) {
  return BitGo.prototype._constants[env];
  }
  - const result = yield this.get(this.url('/client/constants')).result();
  - BitGo.prototype._constants[env] = result.constants;
  - BitGo.prototype._constantsExpire[env] = moment.utc().add(result.ttl, 'second').toDate();
  + const result = yield superagent.get(this.url('/client/constants'));
  + BitGo.prototype._constants[env] = result.body.constants;
  +
  + BitGo.prototype._constantsExpire[env] = moment.utc().add(result.body.ttl, 'second').toDate();
  return BitGo.prototype._constants[env];
  }).call(this).asCallback(callback);
  };
  