Improved readme, installation instructions, and documentation.

As promised, here we go :-)

Use the _"View file @ ..."_ link provided by the GitHub PR user interface to see the final result.

Proposed procedure:

1. Let me know what you think and want to change or what you don't feel comfortable with.
1. I'll _add_ commits to this PR.
1. Once we're happy, I'll rebase + squash commits into a single to remove useless history.