Create mobile-nav-android

Addresses following issue: 

CSS animations are supported by Android devices — but only if a single property is changed. As  soon as you try to animate more than one property at once, the entire element disappears. In non-native Android  browsers, the element will be visible for the duration of the animation, but will hide immediately after it’s finished.

So when you target android users with your webapp, you should this css file instead of the default one.