Allows nested parameter attributes

So previously, when you had a attribute like this:

    address[city]

It would place it in the form like this:

    params[address[city]]

Which is not correct, and won't work with the API correctly.  So what we
want is this:

    params[address][city]

This change does just that.  It should also work for parameters like
this:

    address[phone_numbers][work]
    address[phone_numbers][home]
    address[phone_numbers][cell]

And array values:

    phone_numbers[]

Should be all we need to do get that to work.

QA Plan
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Not actually sure...