landing: "edX Platform" --> "EdX Platform" (#2505)
Merge pull request #2522 from Stanford-Online/sef-2505-edx-readme-homepage-fall2012

landing: "edX Platform" --> "EdX Platform" (#2505) -- FALL2012
Merge branch 'fall2012-master' of github.com:Stanford-Online/class2go into fall2012-production