code: function getNewVersions() {
    return getTags()
      .then(tags => {
        var newVersions = []
        for(tag of tags) {
          if (semver.gt(tag.name, update.latest) || (
              semver.eq(tag.name, update.latest) && (semver(tag.name).build[0] || 0) > (semver(update.latest).build[0] || 0)
            )) {
            newVersions.push(tag)
          }
        }
        newVersions.reverse()
        // order versions from lower to greater
        console.log(chalk.blue('New versions available: ' + (newVersions.map(v => v.name).join(', ') || 'none') + '.'))
        return newVersions
      })
      .catch(e => console.log(e.stack))
  }
docs: Filters bootswatch versions greater than latest update defined in update.json.
  @return {Promise} Promise to be resolved with new versions.