Add comment to kathjax.py to update references

Summary: I'm not sure if this is the right place to check this in, so let me know if there's a better place.

Test Plan: None, it's a comment.

Reviewers: alex

CC: alpert

Differential Revision: http://phabricator.khanacademy.org/D5213
Update comment
Put fallback on set-sol tag instead of on template

I broke this a while ago... not convinced this is how it should be but at least this way it works and you don't need to type `0`.

Fixes #114487.

Test Plan:
Answered both of multiplying_and_dividing_rational_expressions_4.html?seed=48&problem=B-over-A-and-C-over-BC and multiplying_and_dividing_rational_expressions_4.html?seed=49&problem=B-over-A-and-C-over-BC successfully.

Auditors: eater
add calculator, fix #118177
Merge pull request #118493 from mauk81/patch-6

add calculator, fix #118177
Use modern blue/red colors

Auditors: eater
Don't show unrelated videos

For a while, I've been seeing a steady stream of reports of people seeing the wrong related videos. At least one culprit seems to be that we weren't properly clearing out related videos in mastery challenges for problems where the user was already mastery2 or mastery3. In that case we don't want to show them any video, but instead we were leaving behind the videos from the previous problem.

Test Plan: It was painful, but crank down the MIN_TIME_ELAPSED_FOR_MASTERY_INCREASE in missions/recommender.py and do lots of practice and mastery tasks until randomly getting a mastery challenge with an exercise in practiced or mastery1 followed by an exercise in mastery2 or mastery3 within the same MC. Some logging was helpful to confirm this condition. Before this change, the second exercise would retain the related videos from the first. After this change (and repeating the repro steps again), the videos disappeared when the second exercise was rendered.

Auditors: benkomalo
ensure that numbers differ from sorted numbers, fix #118660

alternative fix
Merge pull request #119238 from mauk81/patch-7

ensure that numbers differ from sorted numbers, fix #118660
Add pau support! http://xkcd.com/1292/

Test Plan: http://exercises.ka.local/utils/test/answer-types.html

Auditors: csilvers
Merge branch 'add_comment'
Add a comment describing this pau craziness

Test Plan: none

Auditors: csilvers
Mathy equals sign

Auditors: alex
Make click-to-add-point work in IE8

In IE, the VML "canvas" itself wasn't getting mouse events. It seems you only get mouse events on objects that are filled (or if you carefully click the ouline of an unfilled object). Otherwise, the event gets passed to whatever's under the canvas (in our case, sometimes an image). If there's no image, then the canvas gets the event after all. Gotta love IE. The result is that click-to-add points weren't working when a background image was set. This commit adds a big filled in (yet invisible) rectangle and hooks the click handler up to it. This is actually consistent with the other invisible shapes that roam around graphie.mouseLayer, so it doesn't feel like too much of a hack.

Test Plan: Use testrender.html to create a scatterplot in IE8 w/ background image. Click to add points.

Auditors: jack
Fix a unit test

Test Plan: http://exercises.ka.local/utils/test/?testNumber=2

Auditors: alex
Delete calculus util unit tests

We can't quite yet delete the calculus utils. One exercise still depends on them. (But not for long...) But the things that one exercise needs aren't tested and some of these tests are failing.

Test Plan: none
Tabs -> spaces

Test Plan: none

Auditors: alex
All the unit tests pass!

Test Plan: http://exercises.ka.local/utils/test/

Auditors: alex
One set of unit tests to rule them all!

Test Plan: http://exercises.ka.local/utils/test

Auditors: alex
Fix typo and global var

Test Plan: http://exercises.ka.local/utils/test

Auditors: peter