Test EmptyLinesAroundClassBody on singleton class
Spec for Token#to_s

Token#to_s was introduced in https://github.com/bbatsov/rubocop/pull/8
and seems untested forever. I assume it was introduced for debugging
purposes.
Test RedundantSelf with class methods, too
Test LiteralInCondition on post-loop while/until
Spec deprecation of -e and -s options flags
Remove options specs for RuboCop v1.0.0
Spec for passing an ambiguous formatter name
Don't check if the configuration option is nil

The default value for AllowedVariables (per default.yml) is `[]`.