GitHub地址：https://github.com/SnapKit/SnapKit
中文说明：http://www.hangge.com/blog/cache/detail_1097.html
- 例子
let redView = UIView()
redView.backgroundColor = UIColor.red
self.view.addSubview(redView)
redView.snp.makeConstraints { (make) in
make.width.height.equalTo(50)
make.center.equalTo(self.view)
}
- SnapKit设置百分百
//宽度为父view的宽度的一半
make.width.equalTo(_containerView.mas_width).multipliedBy(0.5);
