Add support for HTML5 context menu

Ref.

* http://www.paciellogroup.com/blog/2014/08/what-aria-does-not-do/?utm_source=html5weekly&utm_medium=email
* https://hacks.mozilla.org/2011/11/html5-context-menus-in-firefox-screencast-and-code/
* http://davidwalsh.name/html5-context-menu
* http://blog.teamtreehouse.com/building-html5-context-menus
Update build process
Merge branch 'contextMenu'

* contextMenu:
  Update build process
  Add support for HTML5 context menu
Release 0.4.10