More robust get_registry_record.

Previously if a record had a value of 'None', then get_registry_record would
fail with KeyError. This is now fixed.

I also added a more helpful error message that, in case you passed an
inexisting record name, prints a list of available records.

Lastly I threw some code around to make it prettier.
docs on how to get/set member properties
minor doc addition
more gitignores
we are using manuel in tests, so we should depend on it
Change import grouping style recommendation to follow PEP8
Updates to the style guide based on mailing-list and IRC discussions.