Updates Model tutorial so that validation works

[chadchabot]

Why:

• The What is a Model? tutorial did not work as expected when going through the validation example because validation errors no longer raise error, they raise invalid. Additionally, invalid is only triggered by default during a call to Model.save, while Model.set requires setting the validate option to true.

This change addresses the need by:

• Changing the event trigger from error to invalid.
• Adding the {validate: true} option to the Model.set calls in the validation example.
• Also cleaning up some trailing white space.

Side effects of this change:

• n/a

Issue link:

• n/a

[PeterDaveHello]

I'll respectfully suggest you to move the fix of trailing white space to a separate commit next time, to have a better commit log, thanks.

[PeterDaveHello]

@thomasdavis @dcki @pdcamilleri guys would you like to have a quick review on this PR? Thanks!

[dcki]

Sorry but TBH my last experience attempting to contribute to this project was very poor. Have you added any kind of guidelines for contributors? Until then, I'm staying out of this.

[chadchabot]

Not a problem @PeterDaveHello. I had initially kept them as separate commits, but merged for brevity.

I've separated them and will resubmit.

[PeterDaveHello]

@dcki sorry not. @chadchabot sorry that I don't use that lib, it'll take more time to merge, I'll need some other contributors to help me review this change, do you know anyone else can help? Thanks.

[dcki]

Sorry for all the stuff I've been saying. The truth is I still have very little experience with open source collaboration. While I'm surprised with the way things work, I shouldn't be so quick to be critical given that I am so inexperienced.