changed max-width of css3 switch for better looking in new ipad (or later).

 When max-width is 700px, the navigtion area is in the left side
of screen and very narrow. Changing max-width to 830px , as i tried,
which is best suitable, could make navigation area in the upper of the
screen in new ipad (or later).

picture when max-width is 700px:
![before](http://landerlyoung.github.io/assets/storage/for_ipad_before.jpg)
picture after max-width adjusted to 830px:
![after](http://landerlyoung.github.io/assets/storage/for_ipad_after.jpg)