== String#snakecase

  require 'facets/string/snakecase'

  '/my_module/my_class/'.snakecase.assert == '/my_module/my_class/'
  'MyModule::MyClass'.snakecase.assert == 'my_module/my_class'
  '::MyClass'.snakecase.assert == '/my_class'
  'URI'.snakecase.assert == 'uri'

