Documentation overhaul

[Marcel Bischoff]

Hi all.

As Ryan has identified that the online documentation needs work, I'm
hereby volunteering to give it a go. Since there appear to be quite
specific views on how everthing here needs to be, I'm asking in advance:

- Is that in everyone's interest?

- Is there already someone working on it?

- Where should the final documentation be located: separate website,
  GitHub wiki, GitHub pages, readthedocs.org, something else?

- In what format should the documentation be written: HTML, Markdown,
  TeX, whatever? I prefer Markdown.

Please let me know what you think.

Best,
Marcel