Don't count empty answer as wrong

Auditors: eater, cbhl
Use 'number' input to use the width: 80px CSS rule

Auditors: eater, cbhl
Multiple-choice-y stuff

Auditors: eater, cbhl
Actually add radio.js and another fix

Auditors: eater, cbhl
Remove console.log line

Auditors: eater, cbhl
Allow loading MathJax asynchronously

(and configuring separately, if you so desire.)

Auditors: eater, cbhl
Enable table support in marked.js

Auditors: eater