Possible modifications

Added an html5 tag library, (skeleton still defaults to the standard html library)
Updated jquery and bootstrap library versions in the skeleton, 
Added js, css and images directories in the skeleton. You might want to put them all under a static directory. 
Added "role" as a default attribute to tags (You may or may not want to keep that). 
Added an add-attribute function which just pushes a new attribute into a specific tag. (You may or may not find this useful)
Added the ability to set language, doctype and charset to html and page. Doctype now defaults to html rather than html4.01