util for updating cartodb visualization
create visualizations app and amend utils to use this
CLOSED - task 127: Add db ip cache table to main 
https://github.com/DigitalCampus/django-oppia/issues/issue/127
Fix cartodb update to use new viz model
CLOSED - task 125: Add size and other data to the media model 
https://github.com/DigitalCampus/django-oppia/issues/issue/125
CLOSED - task 113: Not removing old versions of courses from upload dir 
https://github.com/DigitalCampus/django-oppia/issues/issue/113
CLOSED - task 124: Write utility script to test existence of media files
at the given urls 
https://github.com/DigitalCampus/django-oppia/issues/issue/124