Add celery integration and upgrade javascript

[runyaga]

• Upgrade to latest mediaelementjs
• Add collective.celery integration (requires latest collective.celery pull request)
• If x-send-file is being used opt out of that on stream view (requires latest of that package as well)

[djay]

@runyaga would have been nice to split that into different PRs.
I'm assuming it still works with p.a.async right?

[djay]

@runyaga also whats the reason to opt out of x-send-file? I specifically made it work with wc.media if I remember it right?

[runyaga]

yes it should still works with p.a.async.
we only have to disable x-sendfile for the streaming view.
when GET the media file directly it uses x-sendfile
will not be able to break up until smaller PR for awhile.

[djay]

@runyaga why do you want to disable x-sendfile for the streaming view. We used it successfully with streaming and it enabled much better scaling due to HAproxy or other loadbalancers not being able to know that zope is capable of handling another request even if it is streaming.

[runyaga]

@djay nmaier/mod_xsendfile#37 appears others are having issues with range support. we cant get range support working. we hope to move to nginx in the near future for this project.