Added the ability to switch extensions
Warn people about the pillow dependency sinc it seems to throw hard to diagnose errors when pillow isn't installed.
WIP
Merge branch 'master' into pf-new-images

Conflicts:
	utils/make_thumbs.py
Made the number scrubber symmetric

Summary: Uses CSS3 transforms (browser support >= IE9)

Test Plan: Screenshot

Reviewers: pamela, jlfwong, john

Reviewed By: john

Subscribers: #cs

Differential Revision: http://phabricator.khanacademy.org/D14259
Preserve href attribute so browser knows links are visisted

I tried the same trick on the internal links but it doesn't work there.
I think the actual visited state changes when the page loads, which doesn't happen for internal links.

Test Plan:
- Create a new unvisited link, make sure it shows up in blue
- Click it, make sure link shows up as purple.

Auditors: pamela, john
Re-building the images and script changes

Test Plan:
- Go to /cs/new/webpage
- Insert an <img>, see new food and landscapes categories show up
Moved oh-noes-guy out of the output frame and into the main page

Conflicts:
	css/output/style.css
	css/ui/tipbar.css
Re-ordered linting flow so that testing always occurs after injecting the code

This change was made because the webpage tests should occur against the DOM,
and the DOM must built built by injection, so that any scripts which assume document
refers to their document run correctly
WIP
Separated out testing
Implemented update throttling
Will send a new update when the last one is finished rendering.
This should make the output more responsive on fast pages and slow down appropriately on
big projects
WIP
T3300 - Debounce tests

Summary:
Separated out testing
Implemented update throttling. Will send a new update when the last one is finished rendering. This should make the output more responsive on fast pages and slow down appropriately on big projects
Debounce tests

Reviewers: pamela, john, brian

Subscribers: #cs

Differential Revision: http://phabricator.khanacademy.org/D14274
Made it explicit which tooltips show up during playback.

Summary: This is paired with an upate to webapp

Test Plan: watch a video

Reviewers: pamela, john, brian

Subscribers: #cs

Differential Revision: http://phabricator.khanacademy.org/D14306
Fixes to support CSS resizing

Test Plan: In webapp commit

Reviewers: pamela, john, brian

Subscribers: #cs

Differential Revision: http://phabricator.khanacademy.org/D14349
Touch ups
Remove dangling console.log
Fixed tipbar tip number handling bug
Remove old Blockly logic, bring in new Structured Blocks logic and dependencies.
Add in CSS build, as well.
Bring back in-iframe styling for output.
Restored some CSS styles