ALButton 介绍
ALButton 是 UIButton 的子类，添加了一些功能，减少 UIButton 自定义外观和行为的行数，并且添加了一些 Swfit 的优势。
三种初始化方式：
//- 1. Full Initialization
let style = ALButton.ButtonStyle()
//-- set style
let myButton = ALButton(title: "Button Title", style: style, touchUpInsideHandler: {
(sender ) in
//-- Implement touch up inside event here
})
//- 2. Simple initialization with style:
var style = ALButton.ButtonStyle()
//-- set style
let myButton = ALButton(title: "Button Title", style: style)
//- 3. Short initialization
let myButton = ALButton(title: "Button Title")