Backbone.Model::pick isn't schema aware

[forivall]

This is a minor issue and I will fix it.

Backbone = require 'backbone'

class A extends Backbone.Model
  urlRoot: '/api/as'
  schema:
    b: -> ['belongsTo', B, manual_fetch: true]
  sync: require('backbone-http').sync(A)

class B extends Backbone.Model
  urlRoot: '/api/bs'
  schema:
    a: -> ['hasOne', A, manual_fetch: true]
  sync: require('backbone-http').sync(B)

a = new A({b: {id: 1}})
a.get('b_id') # => 1
a.pick('b_id') # => {}   SHOULD BE {b_id: 1}