Removed outdated translations from the official list
Added custom format page to translation component
Link from introduction section
Small fixes
Cleanups
Fixed version for composer install
Improvements based on comments
Extra improvements based on comments
Fixed wrong indentation
Improved custom formats article based on comments
Added note about exporting SYMFONY_ENV
add link to form testing chapter in test section
Moved 'contributing' images to their own directory
fix name of the Yaml component

The component name that is used in the code as well as in the issue
tracker used by the symfony/symfony repository is Yaml (instead of
YAML). Therefore, this should also be the name being used in the
documentation.
replace "Symfony2" with "Symfony"
Added a note about the lacking features of Yaml Component
Fixed code highlighting
Caution that roles should start with ROLE_

In order to save someone else a few hours of frustration make it clear that the ROLE_ preface is not just for show.
Added a note about the side effects of enabling both PHP and Twig
Add formatting, links, and clarity