Style fixes

See line notes!
I moved `.announcements` and `.link-spanner` from elems.scss and put them in objects.scss instead. elems.scss is only meant to provide styles for built-in html elements (e.g. h1), which require defaults. User-created "objects" (the meaning of "object" here is a longer conversation, but just go with it), the selectors for which have higher specificity, get their own file.