Merge pull request #30 from codefellows/br-edits

Hide and nest hints. Rearrange reading assignments.
Close #32 Chapter 3 needs more formatting, before students access today
Close #29 Students are still using system git
Merge pull request #33 from codefellows/erik_edits

Close #29 and #32
Merge master
Change 'a post' to 'an article'
Convert post<space> to article<space>.
Convert <space>post to <space>article.
Convert Post to Article.
Convert _post to _article.