Create function to decompose phylogenetic tree according to designated nodes

[caseywdunn]

Originally reported by: Casey Dunn (Bitbucket: caseywdunn, GitHub: caseywdunn)

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Build the function decompose based on the following template.

#!r

#' Decomposes a single tree into a series of subtrees designated by internal
#' node numbers
#' 
#' @param phy The tree to be decomposed, as an ape phylo object
#' @param x A vector of internal node numbers. The tree phy will be cut on each branch 
#' that subtends each of these nodes.
#' @return A list of phylo objects 
decompose <- function( phy, x ){}

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• Bitbucket: https://bitbucket.org/caseywdunn/hutan/issue/2

[caseywdunn]

Original comment by Casey Dunn (Bitbucket: caseywdunn, GitHub: caseywdunn):

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if x is empty, then it returns a list with one element - the original tree.

[caseywdunn]

Original comment by Casey Dunn (Bitbucket: caseywdunn, GitHub: caseywdunn):

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decompose now passing test, re issue #2. Still need to clean up node names after decomposing.