NewTailReader scopes the passed in reader to just the last N lines passed in.

NewTailReaderWithDelimiter scopes the passed in reader to just the last N lines passed in In this case a "line" is defined by the passed in delimiter.

TailFile returns last n lines of the passed in file.

ErrNonPositiveLinesNumber is an error returned if the lines number was negative.

SizeReaderAt is an interface used to get a ReaderAt as well as the size of the underlying reader.