WIP: Week 1 English cleanup

This is similar to the editing I did for Programming Basics Part 1. According
to the contributor guidelines, you would like to know about work being done.

I am looking to enforce existing HTML usage, and rewrite some slightly awkward
phrasing into hopefully more idiomatic English. I try and correct spelling and
grammer mistakes where I find them.
Merge pull request #36 from mateor/sp

WIP: Week 1 English cleanup