scrape group membership
that date meant start of job title
we're not interested in title_start_date yet
parse start/end dates for former members
break up parsing of tables
some parties have no former members
scrape independents
is_independent flag
vote cdep-id is not chronological :(
all member objects have start_date and end_date
group name and short name
allow for missing columns
join membership intervals
mp_group_membership.interval column
psycopg2 adapter for infinite date ranges
delete memberships if their parents are deleted
import memberships into database
dump/load date range values
short name for independents group
format dates using babel