Determine whether splits are compatible (concave); i.e. they can both occur
on a single tree.
Usage
SplitsCompatible(split1, split2)
Value
SplitsCompatible() returns a logical specifying whether the splits
provided are compatible with one another.
Arguments
split1, split2
Logical vectors listing leaves in a consistent order,
identifying each leaf as a member of the ingroup (TRUE) or outgroup
(FALSE) of the split in question.