Add a df -h view which does not have a route

The point is for students to put a route on this method. There are also lots of
comments and hopefully interesting things to entice students to explore the app
and python.
Add and change comments to be more helpful

Changed according to Jordan's advice on the comments for PR #9.
Also changes the jinja 'safe' filter to 'escape' since that's actually
what we want.
Fix commas in comments to students

Commas can be tough.
Merge pull request #9 from DevOpsBootcamp/df

Add a df -h view which does not have a route