qunit-fixture is not reset between tests properly

[asapach]

93 broke some of our tests which relied on the previous behavior of #qunit-fixture being reset on testStart by the adapter.

The tests basically do this:

QUnit.module("Test suite", {
    beforeEach: function () {
        $("#qunit-fixture").append(fixtures);
    }
});

The problem seems to be that QUnit begin handler runs before the adapter begin handler, which means that QUnit is not able to store QUnit.config.fixture element, because it's not created yet. So the #qunit-fixture element is not restored properly.

Here's the repro: https://github.com/asapach/karma-qunit-fixture

@Krinkle, could you please take a look?

[asapach]

Created a PR to fix this: #106