Change document type from scrartcl to article

[tdealtry]

I was getting the error with my tex setup (tex live 2016 through mactex):

! Class scrartcl Error: undefined old font command `\tt'.

Even if this works for you now, it will almost certainly stop working with future distributions.
There are a couple of ways of fixing this:

1. Change the document type from scrartcl to article
2. Define \tt as something that works

This pull request uses option 1.