general copyedit

- typos: "effect" --> "affect", "left of" --> "left off"
- use semantic linebreaks: http://rhodesmill.org/brandon/2012/one-sentence-per-line/
- eliminate comma splices: http://en.wikipedia.org/wiki/Comma_splice
- minor rephrasing of a few passages for increased clarity
Merge pull request #2 from waldir/patch-1

general copyedit