Replace hardcoded PSR index

When/if https://github.com/php-fig/fig-standards/pull/369 is merged, we will be able to use that file directly instead of maintaining yet another list of all PSRs. I know we're getting a new site at some point but these are all steps forward for now. It looks a bunch better, simplifies the FAQ, etc. I also dont assume the website will go in without a hitch first time so cant hurt to make small improvements now.

It looks pretty cool. Lets click the green.

![screen shot 2014-11-05 at 6 20 51 pm](https://cloud.githubusercontent.com/assets/67381/4929169/69c6fea0-654e-11e4-8827-b42596dcc763.png)