clamped methods of BaseRGBColor does not work as expected #64

Hi

It seems the clamped method has issue when class has been initialized with is_upscaled=True

>>> from colormath.color_objects import sRGBColor
>>> rgb = sRGBColor( 15,45,65,is_upscaled=True)
>>> rgb
sRGBColor(rgb_r=0.058823529411764705,rgb_g=0.17647058823529413,rgb_b=0.2549019607843137)
>>> rgb.rgb_r
0.058823529411764705
>>> rgb.clamped_rgb_r
1 << expecting 15

The change in BaseRGBColor._clamp_rgb_coordinate would fix the issue:

< return min(max(coord, 1), 255)
> return min(max(int(math.floor(0.5 + coord * 255)), 1), 255)

Thanks