This includes Week 6 homework

I renamed the html_render.py file from the one I was noting down during optional class, so that's the reason for all the deletions and insertions. I tried to create it without looking at the notes as much as possible, but classes are pretty confusing, so a lot of it is very similar. 
you just call os.rename(), and it will raise an exception (IOError, maybe?) if the file isn't there -- remember IEAFP (It's Easier to Ask Forgiveness than Permission) -- plus, less code to write.