feat(Effects): Introduce new Effects testing module

[MikeRyanDev]

Introduces a new testing module for @ngrx/effects that is designed to work well with marble testing.

Example usage:

import { provideMockActions } from '@ngrx/effects/testing';
import { hot } from 'jasmine-marbles';
import { MyEffects } from './my-effects';

describe('My Effects', () => {
  let effects: MyEffects;
  let actions: Observable<any>;

  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [
        MyEffects,
        provideMockActions(() => actions),
        // other providers
      ],
    });

    effects = TestBed.get(MyEffects);
  });

  it('should work', () => {
    actions = hot('--a--b--c--', { a: SomeAction, ... });

    expect(effects.someSource$).toBeObservable(expected);
  });
});

[brandonroberts]

Needs an integration test

[brandonroberts]

We can add the integration test in the example app after this gets merged

[brandonroberts]

Review is done. Test in the store spec needs to be fixed since the behavior has changed in Rx

[coveralls]

Coverage decreased (-0.1%) to 88.426% when pulling c84425e on chore/ngrx-effects-testing into d176a11 on master.