[issue871] Fix Google Code Bug Importer

Continuation of #50. @paulproteus and I are pairing on a CR and we will merge this tonight.
This is a tracker-dependent value; we want this to be configurable. e.g. from roundup.py:225:

        # Create a lookup set where all the values in here represent
        # status values that "look closed"
        closed_status_set = set()
        for status_name in tm.closed_status.split(','):
            closed_status_set.add(status_name.strip().lower())

    # ...

        'looks_closed': (metadata_dict['Status'].lower() in closed_status_set)