ute difference between successive approximations is less than <code>rombergabs</code>,
or the relative difference in successive approximations is less than <code>rombergtol</code>.
Thus when <code>rombergabs</code> is 0.0 (the default)
only the relative error test has any effect on <code>romberg</code>.
</p>
<p><code>romberg</code> halves the stepsize at most <code>rombergit</code> times before it gives up;
the maximum number of function evaluations is therefore <code>2^rombergit</code>.
If the error criter