Document \e, \url. Add a few more comments about mkhowto.
Document \e, \url.
Add a few more comments about mkhowto.

Based on comments from Albert <hat@se-46.wpa.wtb.tue.nl>.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator