Support explicit topic target in send()

[bastienleonard]

Following issue #146:

This is a quick fix for sending to a topic with send():

sender.send(
    message,
    { topic: '/topics/global' }, // can also be { registrationIds: [...] },
    { retries: 2 },
    callback
);

If it looks good enough, I'll add support for the same parameters for sendNoRetry().

[hypesystem]

Seeing as you are changing the possible contents of the second parameter of send, I think it would be fitting to rename it registrationIds -> recipient (likewise, originalRegIds -> originalRecipient). This makes clearer what the variable contains.

It looks good, and it would be nice to support this in sendNoRetry.

Remember to add tests for sending to topics, update the README, and add yourself to the contributors in package.json.

[bastienleonard]

• Make the same change in sendNoRetry()

[bastienleonard]

• Rename registrationIds to recipient

[bastienleonard]

• Return an error if an object with no keys or invalid keys is passed
• Add unit tests

[bastienleonard]

That's all for today. I just realized that I should probably add support for notificationKey.

[hypesystem]

Looks really good! I had a few comments. Other than that I see the following things missing:

• notificationKey support (as you suggest)
• Update README
• Add yourself to contributors in package.json

Thank you so much for your time :)

[bastienleonard]

• Support recipient.notificationKey

[bastienleonard]

• Remove duplication of recipient extraction
• Explicit errors when recipient keys are invalid

[bastienleonard]

(Will update the readme and contributors list after work, if you're OK with the changes)

[hypesystem]

Looks good :) Let me know when you've updated README and contributors, and I will merge :)

[bastienleonard]

• Update the readme. I decided to use an explicit recipient everywhere (e.g. { registrationIds: [...] }), not sure what's your take on this.
• Update contributors in package.json

[hypesystem]

Looks good :) I think the explicit recipient-type is the best model until we make a breaking change, so we should encourage that in the README.

[hypesystem]

Just now released in 0.12.0