Make MethodNodeBase#body_nodes handle empty body
Update feature to match different unparse output
Always format with SexpFormatter
Make sure unparsed source is always just a single line
Update output format in feature (part 2)
Update unparser dependency

- Does not work on Ruby 1.9.2. Time to get rid of it I suppose ...
- Update expected output
Make include work on Ruby 2.0 and 1.9.3
Use generic CodeContext for other nodes
Make tests succeed on Ruby 2.0 and 1.9.3
Fix style and smells