In Curve: Added numerical FD differentiation if derivative is not supplied. Added arc length computation based on the derivative. Added arc length parameterization (but this function is very slow.). In +util: Added fzero_vec.m and integral_vec.m, which call fzero and integral but take vector arguments.

% Creates a matrix of size n,m with the values of val on the diagonals diag.
function A = stripeMatrix(val,diags,n,m)
    default_arg('m',n);

    D = ones(n,1)*val;
    A = spdiags(D,diags,n,m);
end