fix #13697

[skip sauce]
add missing role="menu" attrs to .dropdown-menu elements in docs+examples

Docs audit prompted by #13697.
[skip sauce]
Merge pull request #13700 from twbs/role-menu-all-the-things

add missing role="menu" attrs to .dropdown-menu elements in docs+examples
Update Blob.js to v2014-05-31.

[ci skip]
Update filesaver.js to v2014-05-27.

[ci skip]
Update holder.js to the latest git.

[ci skip]
Run `grunt`.

[ci skip]