Incorporating "flipped" property

[shiffman]

Picking up on #127, we can now add the flipped property to a selection of examples that work with video input. This is a great starter issue for a new contributor!

[shiffman]

Hi @sharellb, it occured to me after our meeting today that this could another thing to work on as you get started with learning about ml5.js development! For this issue, I think it's just a matter of going through the examples and incorporating the flipped property into some (or all?) of them. After that you could do a review of the docs and propose to the web team where we might add infromation about the flipped property (and note how it only works updated version of p5.js, I forget which number exactly!).

Also there is more info in the p5.js discussion! processing/p5.js#6441

@ziyuan-linn anything I might be forgetting about this new feature of ml5?

[ziyuan-linn]

I am for the idea of incorporating flipped in all examples! I think for most use cases, the more natural mirror footage would be preferred.