Acts as Draftable
=====================

Allows a model to save certain attributes into a smaller drafts table.  These are meant to be
temporary modifications until the actual model is saved.  This is very similar to Acts as Versioned.

This example class will create drafts on the title and body fields of Article:

  class Article < ActiveRecord::Base
    acts_as_draftable :fields => [:title, :body]
  end

Here's a sample workflow:

1. Create your model.

  article = Article.new(:title => 'foo', :body => 'bar')

2. Save draft.

  article.save_draft

3. Retrieve latest draft.

  draft = Article::Draft.find_new(:first, :order => 'updated_at desc')

4. Decide you like the draft, and save it.

  article = draft.to_article
  article.save
  
  # notice your draft is now gone
  Article::Draft.find_new(:first, :order => 'updated_at desc')
  # => nil

5. Create a new draft from the saved article

  article = Article.find(1)
  article.title
  # => 'foo'
  article.title = 'bar'
  article.save_draft

6. Load the draft's attributes over the current attributes without saving

  article = Article.find(1)
  article.title
  # => 'foo'
  article.load_from_draft
  article.title
  # => 'bar'

7. Save the draft's attributes over the current attributes

  article = Article.find(1)
  article.title
  # => 'foo'
  article.save_from_draft
  article.title
  # => 'bar'