fails:Dir.exist? returns true if the given directory exists
fails:Dir.exist? returns true for '.'
fails:Dir.exist? returns true for '..'
fails:Dir.exist? understands non-ASCII paths
fails:Dir.exist? understands relative paths
fails:Dir.exist? returns false if the given directory doesn't exist
fails:Dir.exist? doesn't require the name to have a trailing slash
fails:Dir.exist? doesn't expand paths
fails:Dir.exist? returns false if the argument exists but is a file
fails:Dir.exist? doesn't set $! when file doesn't exist
fails:Dir.exist? calls #to_path on non String arguments
