* Fix dead link to USB keycodes doc
Link was dead and the fresher version I could find on usb.org is still older than this one.
Thus, WaybackMachine seems the best option.
* Fix dead link to USB keycodes doc, with 2 options
Give the WaybackMachine link (fresher and for reference of the content of the original link) and the usb.org one (older)
* Generate api docs from source code
* Add a bunch of doxygen comments
* more doxygen comments
* Add the in-progress api docs
* script to generate docs from travis
* Add doc generation to the travis job
* make travis_docs.sh commit the work it does
* make sure the docs script exits cleanly
Leo Wzukw