Revert "Update dataviz.py"

This reverts commit 18c2ab529fdfb590899089565577173b7e783a8d.
fixing @JoeOBrien 's commit within the actual docs
removed _site dir from tracking to remove confusion
Merge branch 'master' of github.com:econchick/new-coder
Merge branch 'master' of github.com:econchick/new-coder
update to new pip instructions, including #104