bugfix for migrating logout button

Context is these Trello cards: https://trello.com/c/lcXDHxGr where the bug was first reported, and the current task, including discussion of this solution: https://trello.com/c/2qItAARv

I'm following a practice I [read about](http://csswizardry.com/2013/04/shame-css/) to keep hacky, short-term solution CSS separate from the rest, so it's easy to find and fix later :)

@nicolashery would appreciate your input on how to potentially remove some of the hackiest bits (noted in the comments of `shame.less`) even for the short-term solution.