Wrong colorspace

Colors in different colorspaces work like RGB:
```rust
let mut image = Image::<u8, Hsv>::new(Size::new(100, 100));
for x in 0..100 {
    for y in 0..100 {
        let mut p = Pixel::<Hsv>::new();
        p[2] = 1.0;
        image.set_pixel(Point::new(x, y), &p);
    }
}

image.save("result.jpg")?;
```

Saves blue: `RGB(0., 0., 1.)` rectangle, instead of white: `HSV(0., 0., 1.)`