Simple and Elegant Timer

中文介绍：打造一个优雅的Timer

##Compare with NSTimer

• No retain cycle
• Decouple with RunLoop
• Support GCD queue
• Support dynamically changing interval
• Support closure syntax

##Usage

###single timer

let timer = SwiftTimer(interval: .seconds(2)) {
    print("fire")
}
timer.start()

###repeatic timer

let timer = SwiftTimer.repeaticTimer(interval: .seconds(1)) {
    print("fire")
}
timer.start()

dynamically changing interval

let timer = SwiftTimer.repeaticTimer(interval: .seconds(5)) { timer in
	print("doSomething")
}
timer.start()  // print doSomething every 5 seconds

func speedUp(timer: SwiftTimer) {
	timer.rescheduleRepeating(interval: .seconds(1))
}
speedUp(timer) // print doSomething every 1 second 

###throttle

SwiftTimer.throttle(interval: .seconds(0.5), identifier: "throttle") {
	search(inputText)
}

###count down timer

let timer = SwiftCountDownTimer(interval: .fromSeconds(0.1), times: 10) { timer , leftTimes in
    label.text = "\(leftTimes)"
}
timer.start()