Merge branch 'hotfix/doxygen'
Gem source

Travis needs it.
Use AppleDoc for compiling the DocSet

Use Doxygen for compiling GitHub pages.
Copyright 2013
AppleDoc and Doxygen compatible comments

Doxygen now uses Markdown. Compatibility easier.
Clean up trailing tabs and spaces
Emphasise the s, rather than quote it

AppleDoc does not substitute the proper apostrophes.
Merge branch 'hotfix/appledoc' into develop