* Bump Rubocop to 0.57.2
* Style/StderrPuts: Use warn instead of .puts
* Style/ExpandPathArguments: Use expand_path('../test_helper', __dir__) instead of expand_path('../../test_helper', __FILE__)
* Style/Encoding: Unnecessary utf-8 encoding comment
* Style/StringLiterals: Prefer double-quoted strings
* Style/AccessModifierDeclarations
* Style/FormatStringToken: Prefer annotated tokens
* Naming/UncommunicativeMethodParamName
* Metrics/LineLength: set maximum line length to 100 characters
* Style/IfUnlessModifier: Favor modifier if usage when having a single-line body
* Style/ClassVars
* Metrics/LineLength: set maximum line length to 80 characters (default)
* Style/AccessModifierDeclarations: EnforcedStyle: inline
