HumanFloatCount for per_sec

[jqnatividad]

@djc here's my attempt to resolve #392.

HumanFloatCount largely mimics HumanCount with the exception that it accepts f64, and truncates the fractional part at 4 decimal places. If the float is a whole number, it doesn't add ".0" to the end.

    #[test]
    fn human_float_count() {
        assert_eq!("42", format!("{}", HumanFloatCount(42.0)));
        assert_eq!("7,654", format!("{}", HumanFloatCount(7654.0)));
        assert_eq!("12,345", format!("{}", HumanFloatCount(12345.0)));
        assert_eq!(
            "1,234,567,890",
            format!("{}", HumanFloatCount(1234567890.0))
        );
        assert_eq!("42.5", format!("{}", HumanFloatCount(42.5)));
        assert_eq!("7,654.321", format!("{}", HumanFloatCount(7654.321)));
        assert_eq!("12,345.6789", format!("{}", HumanFloatCount(12345.6789)));
        assert_eq!(
            "1,234,567,890.1234",
            format!("{}", HumanFloatCount(1234567890.123456))
        );
    }

per_sec uses it, so instead of

210879.6613/s, you'd get 210,879.6613/s

[jqnatividad]

now also rounds to four decimal places and trims trailing zeroes

    #[test]
    fn human_float_count() {
        assert_eq!("42", format!("{}", HumanFloatCount(42.0)));
        assert_eq!("7,654", format!("{}", HumanFloatCount(7654.0)));
        assert_eq!("12,345", format!("{}", HumanFloatCount(12345.0)));
        assert_eq!(
            "1,234,567,890",
            format!("{}", HumanFloatCount(1234567890.0))
        );
        assert_eq!("42.5", format!("{}", HumanFloatCount(42.5)));
        assert_eq!("42.5", format!("{}", HumanFloatCount(42.500012345)));
        assert_eq!("42.502", format!("{}", HumanFloatCount(42.502012345)));
        assert_eq!("7,654.321", format!("{}", HumanFloatCount(7654.321)));
        assert_eq!("7,654.321", format!("{}", HumanFloatCount(7654.3210123456)));
        assert_eq!("12,345.6789", format!("{}", HumanFloatCount(12345.6789)));
        assert_eq!(
            "1,234,567,890.1235",
            format!("{}", HumanFloatCount(1234567890.1234567))
        );
        assert_eq!(
            "1,234,567,890.1234",
            format!("{}", HumanFloatCount(1234567890.1234321))
        );
    }

[djc]

Thanks!