Update dev dependencies.
`noConflict`: Always return the original value.

This fixes an issue where `noConflict` would return `false` if the
global `JSON` object did not exist.
Update the unit tests.

* Wrap the test suite definition in a `defineTests()` function for
  compatibility with asynchronous module loaders.
* Fix a race condition caused by loading and evaluating JSON 3 in
  parallel to the unit tests, as opposed to specifying it as a
  dependency.
* Update the browser test harness.
Check in Spec, Newton, and marked.