Fiddle with readme

From top to bottom:

1. Drop the leading `===`. It is interpreted as an `<hl>`.
2. Wrap the ordered list at 80 chars.
3. Fix all fenced code blocks. Fenced code blocks (denoted by triple-backticks)
   do not require any tabbing beyond that which denotes which block they belong
   in, so place fences in apparently correct locations. The hash mark is a
   convention that indicates a command needs to be run as root, and it appears
   to be unnecessary in most or all cases, so drop it.
4. Use single backticks to denote inline code. Using triple backticks for inline
   code is syntactically incorrect.
5. Make paragraphs flow together. Do not place "Note:" on a line all by itself,
   as it is not a paragraph.
6. Add a blank line after the "code contribution" header, for the sake of
   consistency and niceness.

Also, fiddle with the wording throughout the readme.