contains, rasterize, fast_rasterize

contains for triangle2: signedness is taken from non-zero area values (instead of A0 by default, which is zero if checking e.g. pos1 of triangle. this lead to only one of the vertices of the triangle being evaluated as "contained" no matter the size of the eps.) removed target bounding box (limits) from rasterize function added fast_rasterize, which uses edge functions, does not return barycentric coordinates (still simple traversal but faster than rasterize)