Clean up and changes (weeks 1-6)

I did what I could to keep the commit feature-specific so that you could make your own decisions about which commits you wanted to keep. I also have an unsquashed branch, with [the original 50+ commits](https://github.com/mateor/MOOC-material/commits/master1) separated much more finely. If you would rather a pull-request with the even smaller commits, I can do that.

You will also see I separated a commit that added my name to the English translations contributor list. That is so you do not feel pressured into merging it if your standards to do so are not met.

Thanks for the course, I enojyed it.