rubocop: fixed "Nil comparison"
rubocop: fixed "Comparison of something with itself"
rubocop: fixed "Style/TrivialAccessors" - allow predicates
rubocop: set Style/StringLiteralsInInterpolation to double_quotes
rubocop: fixed "Rename is_registered? to registered?"
rubocop: fixed "(...) interpreted as grouped expression"
rubocop: fixed "Shadowing outer local variable"
rubocop: fixed "Unused method argument"
rubocop: fixed "Useless private access modifier"
rubocop: fixed "Useless assignment to variable"
rubocop: fixed "Do not use :: for method calls"
rubocop: fixed "Avoid rescuing the Exception class"
rubocop: fixed "Use a guard clause"
rubocop: fixed "Use the new Ruby 1.9 hash syntax"
rubocop: fixed "Use \ instead of + to concatenate"
rubocop: use "raise" instead of "fail"
rubocop: fixed "Do not prefix method names with get/set"
rubocop: fixed "Inconsistent indentation"
rubocop: fixed "Avoid multi-line ternary operator"
rubocop: fixed "Use nested module/class definitions"