add blank=True to start_date and end_date
begin writing tests
fix some help text
fix management command lazy translations, None-comparison, string interpolation, imports
fix models None-comparison, remove default save method
test Boundary model
add comment about settings.py
make offset error consistent with limit error, fix base_views imports
remove whitespace which makes json different from that generated by python
tidy urls.py imports
add loads of tests