Back to Text, more time, more logging.

Changed summary column back to Text, I misunderstood the exception from
before, was unrelated to the column type, I forgot to remove
unique=True.

Gave the task a higher soft time limit, that first run takes up over a
minute sometimes.

Added more logging statements to task.

Task returns a list instead of a set. Sets aren't hashable, which is
needed for JSON, which is used to store results from the Celery task
according to config.py.