Number of nodes that must be traversed to navigate from each edge to
each other edge within a tree
Usage
EdgeDistances(tree)
Value
EdgeDistances() returns a symmetrical matrix listing the number
of edges that must be traversed to travel from each numbered edge to each
other.
The two edges straddling the root of a rooted tree
are treated as a single edge. Add a "root" tip using AddTip() if the
position of the root is significant.