Enabling showDiff for assert's equal and notEqual methods. Closes #790

[lucasfcosta]

This aims to close #790.

As explained on this post the equal and notEqual methods on the assert interface, which called Assertion.assert directly, didn't have the showDiff flag turned on and that would make their error messages look different because of the way the test runner showed results.

In order to make that behavior consistent with the equal related methods on other interfaces, I enabled the showDiff flag for these assertions too.

I didn't add any tests since this was a problem related to the test runner and not ours.
Please read the post I linked above for more details.
Thanks everyone 😄

[meeber]

LGTM!

[lucasfcosta]

Well, actually I was taking a look at #574 and I noticed this would not necessarily be needed, since the new default behavior of showDiff on 4.x.x will be to be turned on if it is not explicitly defined as false.

However, I'd like to keep this explicit just to make sure the behavior will still be consistent with the other equal methods, since they explicitly set showDiff to true.

Let me know if you prefer thrusting on the default behavior instead of adding an explicit true value for the showDiff flag.

[meeber]

I prefer to keep it explicit for reasons of consistency.

[keithamus]

Yeah, let's keep it explicit. LGTM