Refers #163 -- Add sponsors listing page
Refers #163 -- Update style to match @mschufferth's wire frames
Merge branch 'develop' into feature/sponsors-page
Refers #163 -- Update stylesheet to provide the same space for every logo.
Refers #163 -- Sponsor ordering should be deterministic.
Merge pull request #164 from EuroPython/feature/sponsors-page

Refers #163 -- Add sponsors listing page
Refer #163 -- Fix last item in sponsorlevel