LRGlowingButton 介绍
LRGlowingButton 是 UIButton 的之类，可自定义发光颜色，用于替代默认的 showsTouchWhenHighlighted
示例代码：
LRGlowingButton *button = [LRGlowingButton buttonWithType:UIButtonTypeCustom];
button.glowsWhenHighlighted = YES;
button.highlightedGlowColor = [UIColor whiteColor];
[self.view addSubview:button];
LRGlowingButton 官网
https://github.com/lightroomapps/LRGlowingButton
