[Enhancement] Adding the ability to apply or discard a subset of keys

[thoov]

We have a fair complex form that we back with the buffered proxy and found that we could "stage" a bunch of changes inside of the buffer and then when the user submits the form apply only the subset that should be persisted instead of the whole buffer.

actions: {
  submit: function() {
    this.applyBufferedChanges(this.get('keysToApply'));
    ...
  }
}
...

keysToApply: function() {
  // logic to determine which keys to persisted
}.property()

[stefanpenner]

I like this idea, I left some suggestions to simplify the implementation.

[stefanpenner]

could you also add an tidbit in the readme?

[thoov]

Thanks for the comments and I will address them :+1:. And yes I will update the readme

[thoov]

@stefanpenner Anything here you still want updated?

[stefanpenner]

Nope looks great. Thanks :)