Improved wording.
Add link to percona website
Add a link to 5.4 patch
Add a link to available bytecode caches
Add links to nginx, php-fpm and apache
Improved wording
Link to speedster advanced instead of standard

Linked to the advanced one because it does the cool file grouping stuff
as well as the minification.
Mention turpentine in the caching section
Split performance out to frontend and backend
Merge branch 'pr/14' into gh-pages