Added `Ray`, `Vec2d` and `Polygon` to `vecmath`
Using type alias for `Polygon` in `PolygonContext`
Using type alias for `Polygon` in `AddPolygon`
Using type alias for `Polygon` in `Context`
Using type alias for `Polygon` in `ColorContext`
Added `Polygons` type alias
Using type alias for `Polygons` in `TweenContext`
Using type alias for `Polygons` in `AddPolygons`
Using type alias for `Polygons` in `TweenColorContext`
Using type alias for `Polygons` in `TweenPolygonsContext`
Using type alias for `Polygons` in `TweenPolygonsColorContext`
Made code consistent with type aliasing
Merge pull request #373 from bvssvni/type_alias

Going back to type alias