在UIbutton中有是三个EdgeInsets的设置：ContentEdgeInsets、titleEdgeInsets、imageEdgeInsets
UIEdgeInsetsMake
里面的四个参数表示距离上边界、左边界、下边界、右边界的距离，默认都为零，title／image在button的正中央
left.titleEdgeInsets = UIEdgeInsetsMake(3, -25, 0, 0);
left.imageEdgeInsets = UIEdgeInsetsMake(0, -30, 0, 0);
具体左边根据需求自己调