docs: function xs(dyn, urlArr, selector, limit) {
    dyn = dyn || false
    var x = scrape.bind(null, dyn)
      // limit the urlArr size for crawling
    if (limit > 0) urlArr = _.take(urlArr, limit)
    console.log("urlArr is", urlArr)
    var promises = []
    _.each(urlArr, function(url) {
      var defer = new Promise(function(resolve, reject) {
        x(url, selector)
          .then(grab.bind(null, url))
          .then(resolve)
          .catch(reject)
      })
      promises.push(defer)
    })
    return Promise.all(promises)
  }