Fixes a teeny tiny typo in a comment.
Catch exceptions on test page

Summary: This makes typing into the box bearable with break-on-exception enabled.

Test Plan: Typed into box; I didn't blow up.

Reviewers: emily

Reviewed By: emily

Subscribers: jessie

Differential Revision: http://phabricator.khanacademy.org/D13314
Update huxley screenshots

Update huxley, and then use the Dockerfile to create new huxley screenshots.

Test plan:
 - Make sure generating new huxley screenshots works
 - Ensure that re-generating huxley screenshots produces no changes

Auditors: alpert
Improve the fonts.less experience

Summary:
Create a fonts.less file which generates identical css to fonts.css, but using
less rules to be more understandable and customizable. For example, add the
ability to change where the fonts directory is located (instead of mandating it
be located next to the less file), and add the ability to disable specific font
formats (like disable EOTs when IE8 support isn't needed).

Test Plan:
 - Ensure that the test page and huxley page still work
 - Ensure that the output of `./node_modules/.bin/lessc static/fonts.less` is
   the same as the original css by running both through
   `./node_modules/.bin/cleancss` and diffing them.
 - Ensure that the huxley screenshots haven't changed
 - Ensure that the build step still works

Reviewers: alpert

Reviewed By: alpert

Differential Revision: http://phabricator.khanacademy.org/D13326
Merge pull request #91 from MandaBrown/teeny_tiny_typo_fix

Fixes a teeny tiny typo in a comment.
added position property to ParseError
Merge pull request #104 from kevinb7/error.position

added position property to ParseError