API for specifying required options for each provider.

[calebd]

[alexito4]

On the same subject, which is currently the fastest way to see the required options and their keys? It would be nice if every provider header file has the required optoins keys ;) simple and effective.

[calebd]

That's a good question. I can certainly put them in the header file. That would even help get them into CocoaDocs. I think I might make a requiredOptions method on SimpleAuthProvider as well so that developers don't use the API and see a crash on some background thread or something. Maybe -[SimpleAuthProvider initWithOptions:] would check the options against required values right away to give you instant feedback.