Cleanup

There's a lot going on here, so let me explain:
-- I began cleaning up some of the lesson 1, 2, and 3 slides, which is where those edits came from.
-- I took the fall schedule off the front page, and moved the devops blurb to the top of the page
-- Replaced 'view page source' with 'edit on github'
-- Updated the headcount chart, and took it off the site (it looks messy and is sad).
-- Added some onboarding newbie docs, which will hopefully be improved. 
-- Added the rest of the exercises to the exercises page. 

@jordane @ElijahCaine @edunham @iankronquist   I can push these once they look good to everyone. 
This is one of the biggest problems actually. If this isn't changed it won't work, and they won't know how to fix it at all.