BAH.  Was completely broken on IE8.
BAH.  Was completely broken on IE8.

I used `keyMap.default` but `default` is a reserved keyword.
(OK as property in ES5, not in IE8 <http://stackoverflow.com/a/5371101/239657>)
And I have only myself to blame - I "simplified" code that correctly used `keyMap["default"]`.
And I didn't run any lint, nor tested on IE.

=> I should really get an automated smoke test.

martindale/mathdown,martindale/mathdown,lynnshahuang/mathdown,lynnshahuang/mathdown,martindale/mathdown,rhythmus/mathdown,lynnshahuang/mathdown,rhythmus/mathdown