Model smart answer nodes as separate embedded objects
Validate node body with SafeHtml
Allow nodes to be created using nested attributes
Split Option into new model

Move the Node and Option classes into the 
simple_smart_answer directory
Require node.rb and option.rb in the edition
Fix issues with cloning a SimpleSmartAnswer to another format

- Only clone nodes if the new edition is a SimpleSmartAnswer
- Copy the body if the edition is being cloned to an answer
Merge remote branch 'origin/master' into simple-smart-answer-node

Conflicts:
	app/models/simple_smart_answer_edition.rb
Correctly namespace the Option model
Use self.body instead of whole_body
Merge remote-tracking branch 'origin/simple-smart-answer-node'