Documentation improvement for $watch, $watchCollection

[atticoos]

This is an important piece for large applications, and one that is often misunderstood.

Tero Parviainen posted a great piece on a brief overview of the difference between reference watchers, collection watchers, and equality watchers.

http://teropa.info/blog/2014/01/26/the-three-watch-depths-of-angularjs.html

I think the docs could benefit from something like this.

[btford]

Why not ping Tero Parviainen and ask him to submit a PR?

[teropa]

Sure, why not. I'll see how this kind of graphic might fit into the Scope doc and make a PR if it seems worth it.