[#122] Rename 'CHANGES' to 'HISTORY' and reformat.
Created by: elbenfreund
This PR moves and reformats the content of CHANGES.md
to HISTORY.rst
in order to be in line with the rest of the project.
The actual content and wording of old release notes has not been changes as we lack the overview to improve on them without unfeasible abmunt of effort. We fixed punctuation and Capitalization though.
Closes: #122 (closed)