Faster login for selenium tests

Instead of navigating through the login page, we just set the
session/cookie data directly.
Don't save screenshots after each unittest

Saving a screenshot takes about 5 seconds per screenshot.  Janet has a
way better way to capture info about failures using saucelabs.
Allow selenium tests to re-use the browser

If the test class sets NEW_BROWSER_PER_TEST_CASE = False, then we will
only create a new browser once per class.  This results in a huge
speedup if there are many test methods.
First steps toward a video controller with playback events. Implement controller.playChunk(). Also update Popcorn.js to latest.
Merge branch 'dev' of github.com:pculture/unisubs into dev
No need for jQuery here.
removed django_nose from installed apps
1934: Fixing subtitling sessions on dev
Force controls for videos in the new editor.
Merge branch 'dev' of github.com:pculture/unisubs into dev
Fix broken event overlapping with video in subtitle editor.
Fix non-positive-integer start times for playChunk()
Move the keydown handling for video control into a new directive aimed at the top-level editor, rather than only in the subtitle list.
Fix undefined reference errors with JSHint. A little too much magic.
Merge branch 'dev' of github.com:pculture/unisubs into selenium_perf
Updated adding a language docs
Update video/subtitle migration dependencies.

This should allow us to migrate the videos and subtitles apps in the correct
order without breaking anything or destroying any data.  I think.
Merge branch 'dev' of github.com:pculture/unisubs into selenium_perf
Merge branch 'staging' into dev

Conflicts:
	apps/accountlinker/models.py
	apps/profiles/views.py
	apps/videos/tasks.py
	apps/videos/types/youtube.py
	optional/unisubs-integration
Docs: add youtube to toc tree