Function format_pretty_hex 

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

Outputs a human readable string like:

let pretty = parse_int::format_pretty_hex(1024);
assert_eq!("0x4_00", pretty);

Floats do not implement LowerHex