Update README.md
[#73635580] Context now stores whole html response
cleanup and sundry
[#73726756] Celery-ified search/collection tasks
[#73213154] config for Celery, Gunicorn
[#73213154] dependencies for virtualenv
cleanup
[#73213154] various changes for Celery support
cleanup
[#73726756][#73768872] continued celery-ification

* AMPQ backend now working;
* added GroupTask model to enable status-checking;
* Celery tasks should use testing=True kwarg to avoid database
weirdness.
[#73769232] fixed QueryString admin FieldError
[#73769058] fixed QueryItem admin AttributeError
[#73635598] revised data model

QueryItem split into QueryResultItem and Item. Items are unique, and
have a unique URL. Items can have multiple contexts, and can be
associated with multiple QueryResultItems. A QueryResultItem represents
an item in a QueryResult, and there can be multiple QueryResultItems
for a given URL. This allows us to record multiple contexts for an Item.
[#73849574] admin for Contexts
[#73849586] admin for Images
[#73849598][#73849608] filtering Items

by QueryEvent and status
[#73849646] view QueryEvents for QueryString
[#73849654] QueryEvent links to a list of Items
sundry admin interface improvements
cleanup models, tasks

added util module as a catchall