txus/to_source

* Do not emit parantheses around non keywords in binary operations (this will beautify source again)
* Add YARD coverage again
* Fix all dm2 metric tools issues
* Mutation coverage!
* Fix parsing errors from ruby parser
  It breaks on def $keyword.
* Report bug about missing Rubinius::AST::SClass#body
* Decide about to support 18-mode or not