Share 'before' hook test environment with child module

[ming-codes]

Tell us about your runtime:

• QUnit version: 2.6.2
• What environment are you running QUnit in? (e.g., browser, Node): browser
• How are you running QUnit? (e.g., script, testem, Grunt): ember-qunit

What are you trying to do?

module('parent', function(hooks) {
  hooks.before(function() {
    this.hello = 'world';
  });

  test('outer', function(assert) {
    assert.equal(this.hello, 'world'); // pass
  });

  module('child', function() {
    test('inner', function(assert) {
      assert.equal(this.hello, 'world'); // fails
    });
  });
});

What did you expect to happen?

Expecting nested child modules to share test environment with parent module.

What actually happened?

Nested child module have it's own test environment object.

[gibson042]

This is a practical issue that would be resolved by implementing #869.

[Krinkle]

I've confirmed beforeEach is shared as expected, and that before still is not.

https://codepen.io/Krinkle/pen/JjXJgoz

Changing this is imho considered a breaking change, but a good one to make in the 3.0 release.

[Krinkle]

TODO: Figure out how we can help users prepare for this ahead of the QUnit 3.0 release so that any difference in behaviour can be smoothened out and warned for.