Add class field support

[cherifGsoul]

For example:

class Person extends ObservableArray{
		greetings = 'Hello';
}

const cherif = new Person();

cherif.on('greetings', function (ev, newVal, oldVal) {
	    // it should be observable, handle change here
});

// Property change trigger the handler
cherif.greetings = 'Hola';

For canjs/can-observable-mixin#79

[phillipskevin]

Hi @cherifGsoul, I still don't see the docs. Maybe you forgot to push them?

[cherifGsoul]

Hi @cherifGsoul, I still don't see the docs. Maybe you forgot to push them?

Yeah I found the commit waiting to be pushed :/

[cherifGsoul]

@phillipskevin The docs are updated, can you review one more time?

[phillipskevin]

Nice job!