The updates for pulling in CodeMirror and other libraries from

node_modules were a little bit incomplete, with the shipped copy of

jsonlint not being 100% compatible with CodeMirror. Christian had begun

to add an adapter to properly interface the parse method, but that file

never made it. This was first apparent in a test failure with our

bundles, but the "My Account" page wasn't doing linting correctly.
I've added in the (missing) jsonlint/index.ts file, which re-exports

jsonlint with a parse() method that's compatible with CodeMirror.
Once we had the linter adapter in place, I noticed that even though

linter errors were getting through to CodeMirror, they weren't showing

up in the editor. The problem was that we had an older version of the

CodeMirror CSS shipped inside our lib/css/ directory, and that didn't

include the right rules for the linter gutter. Rather than just copy

over the newer versions, I've changed it so we include node_modules in

our include path, and added a new 3rdparty.less file that explicitly

imports CSS from node_modules packages. This way when we update our

dependencies, we'll pull in new CSS files automatically.

Opened the "My Account" page and saw that if I put in broken JSON for

  a custom API token, that I correctly saw the error icon in the linter

  gutter.
Ran tests in reviewboard/tests.py