readme error in failedTokens snippets

[yuripaoloni]

This part of the readme is wrong and should be fixed.

sender.send(message, { registrationTokens: registrationTokens }, function (err, response) {
  var failed_tokens = registrationTokens.filter((token, i) => response[i].error != null);
  console.log('These tokens are no longer ok:', failed_tokens);
});

response[i] is not accessible, it should be response.results[i].

Anyway, thanks a lot for the amazing work with node-gcm.

[eladnava]

Hi @yuripaoloni,
Nice find, thanks for catching that, and for your kind words. Fixed in a4df9a3. 👍