fails:String#strip returns a new string with leading and trailing whitespace removed
fails:String#strip returns a copy of self with trailing NULL bytes and whitespace
fails:String#strip taints the result when self is tainted
fails:String#strip! modifies self in place and returns self
fails:String#strip! returns nil if no modifications where made
fails:String#strip! modifies self removing trailing NULL bytes and whitespace
fails:String#strip! raises a RuntimeError on a frozen instance that is modified
fails:String#strip! raises a RuntimeError on a frozen instance that would not be modified
