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.

function alpha = matrixborrow(A,B)

    function y = neg(x)
        y = min(eig(A-x*B));
    end


    x0 = 1;
    while neg(x0) > -1
        x0 = 2*x0;
    end

    opt = optimset('Display','none');
    alpha = fsolve(@neg, x0,opt);
end