Fixed whitepaper page scaling issue (#82)

Fixed issue #82.

The whitepaper \<li\> boxes are still centered, and fit the screen, but aren't exactly the same width. I used CSS flexbox for this, here's how it comes out in semi-responsive mode:

![whitepaper](https://cloud.githubusercontent.com/assets/6946454/2562526/9f302a64-b84f-11e3-86c6-dac3a3e9511f.png)