Make home page scale on mobile devices.

This needs to be tested in some older browsers (*cough cough Internet Explorer*), since I had to use more magic than usual to make this work, but it makes everything scale on the front page, down to about 316 pixels wide. It looks perfect in Firefox and GNOME's "Web" (modern, WebKit-based).

Medium size:

![screenshot from 2013-09-02 18 46 33](https://f.cloud.github.com/assets/1447206/1069849/4bd3081c-1432-11e3-936d-ea7fbf622ba8.png)

![screenshot from 2013-09-02 18 46 27](https://f.cloud.github.com/assets/1447206/1069850/4f2274a8-1432-11e3-8413-54a5255885f8.png)

![screenshot from 2013-09-02 18 46 10](https://f.cloud.github.com/assets/1447206/1069851/5290b4e2-1432-11e3-8539-7283cc30ea11.png)

Small size:

![screenshot from 2013-09-02 18 45 15](https://f.cloud.github.com/assets/1447206/1069853/71173a1c-1432-11e3-87bf-de4ca96a3018.png)

![screenshot from 2013-09-02 18 45 23](https://f.cloud.github.com/assets/1447206/1069854/73d9d3b8-1432-11e3-834e-c1b008255846.png)

![screenshot from 2013-09-02 18 45 29](https://f.cloud.github.com/assets/1447206/1069855/76b99028-1432-11e3-8084-8628124af8d7.png)

![screenshot from 2013-09-02 18 45 37](https://f.cloud.github.com/assets/1447206/1069856/7b9102de-1432-11e3-8dbf-42ca805244aa.png)

![screenshot from 2013-09-02 18 45 57](https://f.cloud.github.com/assets/1447206/1069857/7deb9b20-1432-11e3-9ae5-2ce51fd06216.png)

At full size, it looks identical, except the apps and features lists have equal sized "tiles" (which was necessary to make them line up correctly when floating). There's a more complicated method I could use if you think this looks bad: I could leave the spacers, but remove them when the window gets too small. I would need two sets of spacers though: One for when there's three "tiles" across and one for when there's two. It's not a huge amount of work, but seemed messy.

![screenshot from 2013-09-02 18 49 04](https://f.cloud.github.com/assets/1447206/1069872/fe27a266-1432-11e3-862a-2458528332bc.png)

![screenshot from 2013-09-02 18 49 28](https://f.cloud.github.com/assets/1447206/1069873/00433862-1433-11e3-865c-781692a0fc11.png)