Get the total number of jobs of type
@param {String} qName Queue name
@param {String} type Job type: {wait|active|delayed|completed|failed}
@returns {Number} Total number of jobs
function(qName, type) {
    var client = redis.client();
    var key = 'bull:' + qName + ':' + type;
    if (type === 'wait' || type === 'active') {
      return client.llenAsync(key);
    } else if (type === 'delayed') {
      return client.zcardAsync(key);
    } else if (type === 'completed' || type === 'failed') {
      return client.scardAsync(key);
    }
    throw new Error('You must provide a valid job type.');
  }