Updated Readme for conversion of ArrayModel to Array

The instruction about conversion of ArrayModel to Array is a bit confusing. I think you'd like to mean like this.

--

To convert a Model or an ArrayModel back to a normal hash or a normal array, call .to_h or .to_a respectively.  To convert them to a JavaScript Object (for passing to some JavaScript code), call `#to_n` (to native).


```ruby
    user = Model.new
    user._name = 'Ryan'
    user._profiles = {
      _twitter: 'http://www.twitter.com/ryanstout',
      _dribbble: 'http://dribbble.com/ryanstout'
    }

    user._profiles.to_h
    # => {twitter: 'http://www.twitter.com/ryanstout', dribbble: 'http://dribbble.com/ryanstout'}

    items = ArrayModel.new([1,2,3,4])
    items.to_a
    # => [1, 2, 3, 4]
```