Better support for model.save with partial setting of nested attributes

[ambischof]

Lets say we have the following user:

bob = new MyModel({
   name: {
       first: 'bob',
       middle: 'bill',
       last: 'smith'
   }
})

if you do bob.set({name.first: "Bob"}) you'd get

{
   name: {
       first: 'Bob',
       middle: 'bill',
       last: 'smith'
   }
}

but if you try to do bob.save({'name.first': "Bob"}) you would get

{
   'name.first': 'Bob',
   name: {
       first: 'bob',
       middle: 'bill',
       last: 'smith'
   }
}

In order to avoid unintended consequences, there should be some mechanism to use save the same way you would use set.