Edited #chapters/00_4_acknowledgments.html
Edited #chapters/00_5_preface.html
Edited #chapters/00_7_intro.html
setting acknowledgments, preface, intro not as chapters
Updated atlas.json
putting back in some figure captions
the 'examples' are actually exercises
examples become div data-type-'example'
Merge branch 'master' of git.atlas.oreilly.com:shiffman/the-nature-of-code