Added edge change to TopologyMove for the three edges between the nephew
and the uncle. This does not appear to improve mixing on small tree
examples, with the sampler still getting stuck in local moves, but this
is likely to be at least in part due to the fact that this topology move
does not allow interchanges between a node and its parent. The LOCAL
move of Larget and Simon is currently being implemented (should be in
the next commit), and may resolve some of these issues.
Resolving conflicts.