- Made scrolling of the sidebar not affect the main page by using a
  a combination of overflow:hidden and overflow:scroll.
- Changed the scrollbar of the sidebar to be visible again for
  accessibilty reason and removed the indication gradient because it
  was causing too much issues.
- The main content is no longer limited to 702px, but now uses all
  available space.
- In WebKit based browsers, the scrollbar received custom styling
  making it appear to be outside of the sidebar.
- Changed the background of the code blocks to a neutral color and
  made inline blocks the same color.
- Made inline code blocks inside italic sections not italic.
- Simplified styling of api_stability classes by introducing a common
  class name for the stability levels.
- Fixed various issues related to the green hover background on links.
- Various minor tweaks to paddings and margins.
- Cleaned up numbers in CSS, removing unnecessary units an decimals.