Function format_pretty_octal 

pub fn format_pretty_octal<N: Num + Display + Octal + PartialOrd + 'static>(
    num: N,
) -> String

Outputs a human readable string like:

let pretty = parse_int::format_pretty_octal(1024);
assert_eq!("0o2_000", pretty);

Floats do not implement Octal