Better error reporting

[krzysztof-grzybek]

Hi,
this PR introduces more readable error reporting. It will display message in marble format, like in the screenshot:

  it('should work with a cold observable', () => {
    const provided = cold('-a----b|', { a: 1, b: 2 });
    const expected = cold('--a---b|', { a: 1, b: 3 });

    expect(provided).toBeObservable(expected);
  });

• it prints marble comparison and detailed JSON.stringified test messages below
• if notification is found in the expected TestObservable, then it will match marble character to this Notification, if not, the character will be equal to ?

Additionally, it fixes not.toBeObservable.

Fixes #51, #11

Please let me know what do you think about these changes :)

[xileftenurb]

after a closer inspection, I think the library was designed to be both used by the jasmine ToBeObservable assertion and the RxJS test Scheduler, but the logic for the two ways is nearly completely separated.
so your PR fix the ToBeObservable way of testing,
and mine fix the "TestScheduler" way.

I think the best would be to merge part of our two work so it uses a single codebase for the two way of testing.
I will try to check your code more closely to see how to fix the TestScheduler from your code

[xileftenurb]

Ok, I checked again, and I realize that there is no link between the two style of marble testing.

It is virtually like if there was 2 library in one.

I don't think there is much value to keep these 2 part together. It would be more sensible to split the library.

In fact, after closer inspection, I see that the TestScheduler of rxjs already give everythings needed to make marble testing, so I will use it direcly instead of using a third party library.

[brandonroberts]

Thanks @krzysztof-grzybek, apologies for the delay. I will cut a release soon

[krzysztof-grzybek]

No worries @brandonroberts , thank you!