Clean unnecessary items. Most of them were included in the file in the
initial push and they don't seem to be relevant anymore.
I tried to go through all our documented workflows for unit testing, docs documentation, package building, virtualenv management, etc etc. All of those should be covered by the ignore keywords I left in. If I have removed something you actively use and want ignored, please shout (or we will add it back in later). I mainly wanted to remove the cruft that nobody knows why it is included, and use more defensive approach for known keywords (full path instead of a global wildcard where appropriate).