Removed loud green color at startpage, added about-us, made documentation 100% width

Yepp,  you read right: I added a long missed about-us page ;) Preview as usual at: http://propelorm.jarves.io/about-us.html

Startpage removed the heavy green: http://propelorm.jarves.io/

Please let me know what you think about the about-us page. Its really important to me, that all active developers that work hard on propel are featured there with the right information, of course with Francois and William. Feel free to tell me different website urls for your profile. Sorting is the same as github shows us in the contribution graph.
Nit-picky thing but here we can use the plural form of "developer" I guess.