Add a TOC to the readme and move rulesets info up
Add a TOC to the readme and move rulesets info up

* Add a table of contents to the readme which has become quite long.
   Auto-generated with: http://ecotrust-canada.github.io/markdown-toc/ and then manually tweaked a little
* Add extra header and indent subheader for rulesets section
* Move the rulesets section up, as it was - by now - quite far down what with all the information on the different integrations

mattyrob/WordPress-Coding-Standards,WordPress-Coding-Standards/WordPress-Coding-Standards,WordPress-Coding-Standards/WordPress-Coding-Standards,paulschreiber/WordPress-Coding-Standards,jrfnl/WordPress-Coding-Standards,WordPress-Coding-Standards/WordPress-Coding-Standards,mattyrob/WordPress-Coding-Standards,paulschreiber/WordPress-Coding-Standards,jrfnl/WordPress-Coding-Standards,mattyrob/WordPress-Coding-Standards,mattyrob/WordPress-Coding-Standards,mattyrob/WordPress-Coding-Standards,jrfnl/WordPress-Coding-Standards,paulschreiber/WordPress-Coding-Standards,WordPress-Coding-Standards/WordPress-Coding-Standards,paulschreiber/WordPress-Coding-Standards,jrfnl/WordPress-Coding-Standards