Add AppData file

Thanks to Richard Hughes and Ryan Lerch for the initial file and forwarding it.
We use the description from our homepage instead and also our screenshots.

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Ignore Sphinx build artefacts

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Merge branch 'master' of github.com:bpython/bpython