Use iOS 7 icon on frontpage (fix #25)

This uses the iOS 7 style Safari icon in place of the old iOS 6 style on the front page of x-tags.org.

Goes from this:
![screenshot 2014-03-28 00 33 18](https://cloud.githubusercontent.com/assets/90871/2546304/1fb18a40-b632-11e3-9afb-3e5905510e97.png)

to this:
![screenshot 2014-03-28 00 33 11](https://cloud.githubusercontent.com/assets/90871/2546305/29f69df6-b632-11e3-86df-cca541c0a8c7.png)