Add tips not on existing tree to the tree via user input,
if they do not have congeners on the tree. This function will generate a
tree, with nodes numbered. For each tip to be added, the user will be asked #' to enter the number of the node they would like the tip to subtend.
Usage
absent_tippr(tree, absent_list)
Arguments
tree
Starting tree; object of type phylo
absent_list
Vector of taxa in the total dataset that are not on the tree
Value
tree Phylo object containing the starting tree,
and all tips that were added.