code: function findValidPhantomJsBinary(libPath) {
    return kew.fcall(function () {
      var libModule = require(libPath)
      if (libModule.location &&
          getTargetPlatform() == libModule.platform &&
          getTargetArch() == libModule.arch) {
        var resolvedLocation = path.resolve(path.dirname(libPath), libModule.location)
        if (fs.statSync(resolvedLocation)) {
          return checkPhantomjsVersion(resolvedLocation).then(function (matches) {
            if (matches) {
              return kew.resolve(resolvedLocation)
            }
          })
        }
      }
      return false
    }).fail(function () {
      return false
    })
  }
docs: Given a lib/location file of a PhantomJS previously installed with NPM,
  is there a valid PhantomJS binary at this lib/location.
  @return {Promise<string>} resolved location of phantomjs binary on success