have Comparator class check overlapping bins

[d-callan]

From microbiomeComputations created by asizemore: VEuPathDB/microbiomeComputations#47

found in #43

The Comparator should check to see if any of group A bins overlap groupB. This is nontrivial because groupA bin could be [0, 1) and groupB [-1, 2) and these should not be allowed.