State of documentation

[tobni]

1. The release changelog is duplicated in CHANGES.rst and docs/releases-notes.rst. These ought to be merged.
2. The repository README.rst contains links that are broken, and repeats (incorrect) supported python versions.
3. Mentions of debian packages and ubuntu should probably be removed, they are not maintained (and their value questionable, all ubuntu distros come with pip).
4. There is a lot of prose that is hard to follow in the docs. I think a good first task is to run it through a spell checker.