optimize "Logo"

Layout on `h1`, decorate on `a` and `mark`.
optimize top margins

* Small screen: relative to logo height
* Medium screen: relative to default line height
* Large screen: relative supplimental width
remove body margins
update dependencies
remove unnecessary clearfixes
decrease contrast slightly

Applied elements are:
  - heading
  - `blockquote`
  - `pre`
  - "Sidenote"
  - "Google Code Prettify"
version 6.43.10