Remove unnecessary import
Remove a bunch of redundant setters

Given that these are all set to default values via __init__ this
is just a waste of space and processing.
Remove commented out code that is no longer necessary
Return an empty unicode string instead of None
Remove dateutil.rrule since it's not used
Now passing PEP8 according to flake8

This will hopefully allow us to develop some easy to follow style guidelines for future contributions.

Fixes #164.
ChangeLog!