v0.2.0

• Value inheritance. Attach any data to a mesh, such as UVs, colors, normals, matrices or your own struct, and it is carried through compute_boolean. Vertices created along the cut get values interpolated from the original faces, and seams stay sharp.
• Any type that can be added and scaled by a real number works (Clone + PartialEq + Default + Add + Mul<Real>, the auto-implemented Data trait).
• Manifold is now generic, Manifold<S = Real>. Use Manifold::new_with_values to attach values and read them from vals of the result. Code using Manifold::new keeps working.