Feature populate active support validation errors

[jimmynguyc]

I thought it would be a good idea to automatically populate the ActiveSupport validation errors when the JSON responded with a ActiveModel::Errors.messages like hash.

E.g. format for json[:errors]

{
    :email => ["can't be empty","is invalid"],
    :password => ["is too short"]
}

It will just ignore when the response is malformed or not a hash.