Clean code

Cleaned code and updated functional documentation

Small upgrade

Here we have added one small condition for agglomeration of two leaves (or two taxa clusters), as follows:
Suppose, two pairs of taxa clusters have identical distance matrix entries (with respect to the NJ / STAR based relative distance matrix). Then which pair to choose?
Here, we choose that cluster pair which exhibits the lowest value with respect to their original distance matrix.

Multi allele gene tree support

1. Supports multi allele gene tree processing
2. Supports NJ_st (Liu et. al. 2011) method execution.

First release

This release contains custom implemented code for the following three methods of species tree construction from incongruent gene trees having ILS / DC.

1. STAR (Liu et. al. 2009) uses the coalescence rank of individual couplets to construct the species tree using a neighbor joining (NJ) approach.

2. STEAC (Liu et. al. 2009) uses the average coalescence time of individual couplets, computed with respect to the input gene trees. The coalescence time is approximated with the branch length information provided in the weighted input gene trees. This algorithm does not apply for unweighted gene trees.

3. GLASS (Roch et. al. 2010) uses the minimum coalescence time of individual couplets, computed with respect to the input gene trees. The coalescence time is approximated with the branch length information provided in the weighted input gene trees. This algorithm does not apply for unweighted gene trees.