Pure python interval calculations.
2013-07-12 v2.0 - naive implementation (NlogN for substructing N out N intervals). Performance test shows 20x difference for substracting 10 000 out of 10 000 intervals between non itree and itree versions
2011-10 v1.0 - naive implementation (N^2 for substructing N out N intervals)
Interval Calculator is licensed under MIT, see MIT-LICENSE.txt.