#645 Polynomial fit extrema determination exception

[David Benn]

Reported by Tom Calderwood in https://www.aavso.org/bug-reports#comment-62491

In ApacheCommonsDerivativeBasedExtremaFinder.java, line 105 is suspect:

int lastIndex = minDerivIndex < obs.size() ? minDerivIndex + 1
                    : minDerivIndex;

The condition should I think be:

minDerivIndex < obs.size()-1

[David Benn]

Fixed as per above solution.