Block support

[garyjohnson]

Thanks for writing this. Wondering if you've considered using block callbacks instead of delegate pattern? It would allow the completion handling code to live near where the alerts are shown instead of being handled in a separate method (that might include a large switch statement if you're showing lots of alerts in a single view). I'd be happy to submit a PR if you're interested in exploring further.

[cwRichardKim]

yea absolutely, i'm happy to take a look at any solution you propose. I think it's tough to completely flip the internals now since there are people depending on this project (which has honestly been my major reason for not changing it).