iPhone5 iPhone6 iPhone6Plus iPad设备 media query（媒体查询）代码.
iPhone < 5:
@media screen and (device-aspect-ratio: 2/3) {}
iPhone 5:
@media screen and (device-aspect-ratio: 40/71) {}
iPhone 6:
@media screen and (device-aspect-ratio: 667/375) {}
iPhone 6Plus:
@media screen and (device-aspect-ratio: 16/9) {}
iPad:
@media screen and (device-aspect-ratio: 3/4) {}