Combine all mentions of documentation

[gvwilson]

Reviewer 3: there could have been a single rule (Document your code and usage) that could encompass the points of both Rules 1 and 2 (Readme, usage) as well as the points about documentation from ‘What we left out’.

[morgantaschuk]

Reviewer 1
I find the relegation of documentation to an additional note rather
than a rule surprising... If software does not have adequate documentation, it will be
harder to maintain (either by the original author or by others).
As mentioned above, documentation is important, and some of the
existing 10 could be merged to make room for this.

Reviewer 3
Finally the ‘What we left out’ section implicitly defines an additional rule (documentation). In this particular case there could have been a single rule (Document your code and usage) that could encompass the points of both Rules 1 and 2 (Readme, usage) as well as the points from ‘What we left out’.

Combined Rules 1 and 2 with the Documentation section from the end, shortened everything a little, and removed non-documentation paragraphs and placed them elsewhere.