Include option to whitelist API keys.

[oparamo]

It'd be useful to have the option to whitelist certain API keys so that requests made with those keys don't get rate limited. For example, if I have some services that need to consume each other, I don't want to worry about limiting my own services.

I could pass a defaultRate function that returns an unreachable rate for requests made by my own services, but ideally I wouldn't want to go through Redis if I can identify an API key I don't want to limit.

Something like this would work I think:

options: {
    whitelist: [ 'myAPIKey', 'anotherKey' ],
}

if (options.whitelist && options.whitelist.indexOf(options.requestAPIKey(request)) > -1) {
  return reply.continue();
}

If this is something y'all would like to include in this plugin, I'd be happy to make a PR that adds this feature and the accompanying unit tests.