Changed function parameter types to match the ones in NSNotificationCenter

[nmarkovic04]

Changed function parameter types to match the ones in NSNotificationCenter so passing the sender is optional in case when you want to attach userInfo to the notification object.

e.g. Kugel.publish("sessionChanged", object: nil, userInfo: ["key" : "val"])

[ldiqual]

@nmarkovic04 Thanks for your PR! At this point I think we should just go with default params so all cases are handled in one entry point. For instance:

public class func publish(name: String, object: AnyObject? = nil, userInfo: [NSObject: AnyObject]? = nil)

Working on this now, I'll update the code and reference this PR when I'm done.