CON-2257 media galleries float fix

Pinging @lizlux (code ownership)
Yes, it comes from the zurb foundation css. 

I was just thinking we could add another element to the selector. I haven't looked into it though and trust your judgement, just thought I'd check to make sure, since it makes my skin crawl a little to see `!important` in there ;). If you think this is the best way then go ahead and merge.