integrated Bob's comments into chapter 4 from former CL

incorporated comments from Vijay about Dartium section

Merge branch 'master' into ch4updates

Cutch feedback and Brian Wilkerson

removed mention of --enable-type-checks and --enable-asserts

put Finder back to your finder

updates from Peter von der Ahe about safari debugging

fixed the content about specifying a browser for JavaScript launches

relatively minor updates to chapter 4

BUG=
R=kathyw@google.com

Review URL: https://codereview.appspot.com/22770045