Merge pull request #68 from kaie/master

multiple changes. Thanks very much kaie!
multiple changes:
* name of first chapter should be different from book title, renamed it to "Introducing Cryptoparty"
* html: added links back from chapters to the main index
* html/css: avoid absolute font size, changed to "font-size: large"
* gitignore: adjust, because all result files are placed into subdirectory named dist