Updating index with further information on how to contribute, minor adjustment to formatting on emberjs credits.

Updating index to reference Fidel, DUEL and Broke.js apps. Included descriptions. Revised intro text.

Repo: https://github.com/jupiterjs/cantodo
Commit: https://github.com/jupiterjs/cantodo/commit/65d43ec7586b0f193b2a9052a4723d286589d26a