Add Chapter: Markdown transformations

[DinisCruz]

implemented at http://plnkr.co/edit/GzLYC7Dycmh3uT9YPK2d

based on code from http://embed.plnkr.co/OyF1xtvyiJmnQ3Hh2I68/preview

using https://github.com/chjj/marked

see also:

• http://ngmodules.org/modules/angular-marked ,
• http://grumpywizards.com/ngMarkdown/
• http://ngmodules.org/modules/angular-markdown-editor
• http://stackoverflow.com/questions/14982422/markdown-with-angularjs-directives
• http://www.anupshinde.com/posts/online-markdown-showdown-editor/