Since `os.FileInfo` is an interface, it is difficult to tweak some of its internal values.

LongStringer is a Stringer that returns the file info formatted in `ls -l` long format.

NameStringer is a Stringer implementation that just prints the name.

QuotedStringer is a Stringer that returns the file name surrounded by qutoes with escaped control characters.

Stringer provides a consistent way to format FileInfo.