message: Fixed incorrect error message
  Summary: The error message stated that the duration must be greater than zero, however zero is allowed.
  Reviewers: arik, alex, jameson
  Subscribers: jameson, ben
diff: @@ -992,7 +992,7 @@ BitGo.prototype.addAccessToken = function(params, callback) {
  // check non-string params
  if (params.duration) {
  if (typeof(params.duration) !== 'number' || params.duration < 0) {
  - throw new Error('duration must be greater than 0');
  + throw new Error('duration must be a non-negative number');
  }
  }
  if (params.ipRestrict) {
  