Minor refactoring
Use class instance variable for Language rules
Allow Ruby expressions as Language rules
Experimental self-hosting PEG parser
Refactor PEGLanguage definition
Experiment use of  symbols instead of references
Use symbols for refrences and names everywhere
Minor refactoring
Introduce Rule as new way of naming expressions
Make #inspect use #arguments
Stop relying on Hash maintaining order
Minor stylistic changes
Alias [] to #new for value objects

http://xaviershay.github.io/writing/docs/ruby_style_guide.html