[BUGFIX beta] Update backburner.js

[tricknotes]

Compare view:

BackburnerJS/backburner.js@22a4df3...325a969

Notable changes are here:

• [FEATURE] configurable setTimeout: [FEATURE] configurable setTimeout BackburnerJS/backburner.js#163
• [breaking] Use native Date.now(): [breaking] Use native Date.now() BackburnerJS/backburner.js#166

[tricknotes]

It seems the test depending on window.setTimeout is failing.

Test failed: run.later: setTimeout should never run with a negative wait
    Failed assertion: stub setTimeout was used, expected: true, but was: undefined
    at http://localhost:13141/qunit/qunit.js:1462
    at http://localhost:13141/qunit/qunit.js:2145
    at http://localhost:13141/ember-tests.js:38124
    at http://localhost:13141/ember-tests.js:37907

https://travis-ci.org/emberjs/ember.js/jobs/107823949

I'll investigate it later.

[rwjblue]

My guess is that this is replacing window.setTimeout after Backburner has already grabbed its copy for _platform, we should update the test to mock the bb._platform prop instead of window.setTimeout.

/cc @runspired

[runspired]

That would likely be the problem, I can take a look late late tonight or sometime tomorrow.