Remove over-eager sponsors styling
Remove over-eager sponsors styling

Each page on the website results in a different class set on `<body>`. In a few cases, these class names were also used for content on the page. This resulted in some styles affecting more than they should.

Summary of this PR:
* Removal of`.sponsors li` -- this was affecting not just the list of sponsors but also the list items in the header nav. The list of sponsors is already styled as it should through the `.showcase` class.
* Removal of `.sponsors ul, .sponsors ol` -- similar to the above, though this actually had no effect on the page at all, as the header-nav overrode these settings for the top list, and `showcase` overrode it for the list of sponsors.

SaladFork/emberjs-website,kpfefferle/website,SaladFork/emberjs-website,kpfefferle/website,SaladFork/emberjs-website,kpfefferle/website,SaladFork/emberjs-website