code: function checkPhantomjsVersion(phantomPath) {
    console.log('Found PhantomJS at', phantomPath, '...verifying')
    return kew.nfcall(cp.execFile, phantomPath, ['--version']).then(function (stdout) {
      var version = stdout.trim()
      if (helper.version == version) {
        return true
      } else {
        console.log('PhantomJS detected, but wrong version', stdout.trim(), '@', phantomPath + '.')
        return false
      }
    }).fail(function (err) {
      console.error('Error verifying phantomjs, continuing', err)
      return false
    })
  }
docs: Check to make sure a given binary is the right version.
  @return {kew.Promise.<boolean>}