inconsistent output when value rounds to zero

[snaar]

These currently pass:

assert_eq!(format!("{:.3}", PrettyPrintFloat(0f64)), "0.0");
assert_eq!(format!("{:.3}", PrettyPrintFloat(0.01f64)), "  0");

But maybe they both should be 0.0? Or at the very least the second one should not be padded to be three characters wide.