edx/edx-platform — pull request #6427 by wedaly (2014-12-31 20:35:38+00:00)
Title: Use disabled property to prevent IE9 users from clicking disabled buttons

[ECOM-849](https://openedx.atlassian.net/browse/ECOM-849)

This PR sets the `disabled` property on disabled buttons (in addition to the usual `is-disabled` CSS class) to ensure that the buttons can't be clicked. This fixes an issue in IE 9 that allowed users to click on disabled buttons.

@AlasdairSwan please review