Use expression editor forsolution
Allow terms with degree > 1 to be defined without using a hash
Merge remote-tracking branch 'upstream/master' into sim-rat-exp-1
Merge remote-tracking branch 'upstream/master' into sim-rat-exp-1
Add hints
Multiple question types
Hint for second question type
Minor rewrite of  hints
Create exercise
Simplify exercise
Term.regex() can be treated by RationalExpression.regex()
Update rational expression unit test
Remove unnecessary extras to regex
Remove unnecessary extras to regex
Add conditions to final hint
Remove debugging
Remove review_mode from interface.js

Test Plan: Crossed fingers

Reviewers: benkomalo

Reviewed By: benkomalo

CC: alpert

Differential Revision: http://phabricator.khanacademy.org/D3793
Refactor exercises so hints are simpler
Remove extra ,

Test plan:
Crossed fingers, or really make lint

Auditors: alpert
Rename katex.less.css to just katex.css

So that a webapp `make clean` doesn't delete it.

Auditors: emily