Fix rotate around custom center

Author: oborozuk1

modules/ILL/ILL/Ass/Shape/Point.moon

@@ -50,9 +50,10 @@ class Point
 
 	-- Rotate the object according the given params.
 	rotate: (angle, c = Point!) =>
-		{:x, :y} = @
-		@x = x * math.cos(angle) - y * math.sin(angle)
-		@y = x * math.sin(angle) + y * math.cos(angle)
+		x_rel = @x - c.x
+		y_rel = @y - c.y
+		@x = x_rel * math.cos(angle) - y_rel * math.sin(angle) + c.x
+		@y = x_rel * math.sin(angle) + y_rel * math.cos(angle) + c.y 
 		return @
 
 	-- Rotate the object according the given params.
@@ -204,4 +205,4 @@ class Point
 		py = a.y + u * (b.y - a.y) + v * (d.y - a.y) + u * v * (a.y - b.y + c.y - d.y)
 		return Point px, py
 
-{:Point}
+{:Point}