v3.1.0

• This version includes breaking changes, but reconciles the Objective-C and Swift apis. Most notable are changes to how acking is done

socket.on("someEvent") {data, ack in
    ack?(1, 2, 4)
}

Would become

socket.on("someEvent") {data, ack in
    ack?.with(1, 2, 4)
}

• The Objective-C method for adding events has been merged with the Swift method.
• The event callback definition has been changed from (NSArray?, ((AnyObject...) -> Void)?) -> Void To ([AnyObject], SocketAckEmitter?) -> Void
• A method has been added to execute an event only once.