Updated doubles hub page logo

bummer designed a new, more metagame-relevant and aesthetically pleasing, one a while ago which is now in use in the threads and such, so i put it in place of the old one on the hub. also replaced the image at media/uploads/tiers/om/doubles
Merge pull request #97 from smogon/updated-doubles-hub-page-logo-665a27

Updated doubles hub page logo