Fix grid. Further HTML cleanup and tweaks.

In #127, @ashashwat reported a regression with the grid option in HTML renderer. The bug was actually because of HTML, or rather, span tags don't support padding when using multiple lines. I made some further fixes, discovered similar issues with output, also noticed changes @shivawu made to the template, after these changes, further cleanup to the CSS was possible. But I also modified the `"Returns:"` part to use a tag instead of CSS.