Implement getKeyDependencies for computed getters

[m-mujica]

class Person extends ObserveObject {
  get fullName() {
    return this.first + " " + this.last;
  }
}

var me = new Person();
me.first = "John";
me.last = "Doe";

draw(getGraph(me, "fullName"));

[m-mujica]

@justinbmeyer the dependency graph of the getter in an array is kinda interesting (this is from the over21 getter example):

[justinbmeyer]

over21 makes sense to me.

[justinbmeyer]

though should it be Person{}.age 6? Is the constructor named?

[m-mujica]

@justinbmeyer The code I used to render that graph is

var People = ObserveArray.extend(
  "People",
  {},
  {
    get over21() {
      return this.filter(function(person) {
        return person.age > 21;
      });
    }
  }
);

var people = new People([
  { id: 1, age: 22 },
  { id: 2, age: 21 },
  { id: 3, age: 23 }
]);

That's why there are no Person instances in the graph; if I wrap the objects in the People array with a Person class I do get the right labels:

I think it's all fine, let me know if you disagree.

I'm going to merge and release 💥