Use latest kuma-lib to fix an issue with Django and hash_ring.
Also install newest version of Django on Travis.
Use placeholder selectors wherever possible

The classes .review-base and .dev-program-pad have been updated to
placeholder selectors because, although they are extended, they do not
appear in markup. This saves 62 bytes of compiled CSS.
fix bug 865863 - remove duplicated styles
Massive minification of all media-dir images
Merge pull request #2400 from jezdez/update-django

Updated some deps.
Merge pull request #2409 from darkwing/optimize-images-again

Massive minification of all media-dir images
Merge pull request #2403 from openjck/use-placeholder-selectors

Use placeholder selectors wherever possible
Merge pull request #2408 from darkwing/865863-remove-css

fix bug 865863 - remove duplicated styles
Fix bug 467346 - Adding prev link to revision history
Ensure the pre_delete signal is only sent once on Document deletion.

Previously it was being sent twice in some circumstances -- once by
Document.delete() and once by the parent delete() method.
add temporary task logger to file for debugging
Merge pull request #2416 from groovecoder/celery-task-logging

add temporary task logger to file for debugging
enable new kuma_task_logger handler in celeryd
Merge pull request #2417 from groovecoder/celeryd-hijack-root-logger

enable new kuma_task_logger handler in celeryd
Merge pull request #2413 from ubernostrum/document-delete-signal

Ensure the pre_delete signal is only sent once on Document deletion.
remove temporary k.task logger
Enabled task sent event.
Merge pull request #2412 from iakshay/bug-467346

Fix bug 467346 - Adding prev link to revision history
Merge pull request #2419 from jezdez/celery-events

Enabled task sent event.