Refactor stakeholders and diversity section

[cwilso]

This fixes #169.

This takes a similar approach to #171, but with a much simpler approach that results in much clearer text.

• the org size et al attributes are included as aspects of stake-holders, rather than having to split into a separate point.
• the aspects of diversity are only mentioned at a high level, and the list is left to a reference to the CoC.

[jyasskin]

Thanks!

[tantek]

This is a big improvement. There's a few editorial nits I'd like to try improving, but can certainly wait to land this and then discuss separately if necessary.

[torgo]

lgtm