Created by: BigBlueHat
This is a documentation-focused commit. The first commit message contains more info--copy/pasted below for "usability":
data-toggle is consistently used throughout Bootstrap for toggling UI related content. The rel attribute is also intended for expressing the relationship between the current URL and the URL being linked to.
In addition (and the initial motiviation for this change), the HTML5 validator [1] marks the HTML as invalid for using unregistered rel values.
Thanks for considering this change.