Added HSL and HSV colors

HSL.go

@@ -0,0 +1,29 @@
+package color
+
+import "math"
+
+// HSL represents a color using hue, saturation and lightness.
+func HSL(hue Value, saturation Value, lightness Value) Color {
+	hue = math.Mod(hue, 360)
+	c := (1 - math.Abs(2*lightness-1)) * saturation
+	x := c * (1 - math.Abs(math.Mod(hue/60, 2)-1))
+	var r, g, b Value
+
+	switch {
+	case hue >= 0 && hue < 60:
+		r, g, b = c, x, 0
+	case hue >= 60 && hue < 120:
+		r, g, b = x, c, 0
+	case hue >= 120 && hue < 180:
+		r, g, b = 0, c, x
+	case hue >= 180 && hue < 240:
+		r, g, b = 0, x, c
+	case hue >= 240 && hue < 300:
+		r, g, b = x, 0, c
+	case hue >= 300 && hue < 360:
+		r, g, b = c, 0, x
+	}
+
+	m := lightness - c/2
+	return RGB(r+m, g+m, b+m)
+}