add TreeConststruction and Consensus modules
implement upgma and nj algorithms"
add parsimony scorer
rewrite and test parsimony score
minor change
add NNITreeSearcher._get_neighbors
complete parsimony method
fix the bug that the nj tree may have 1 child instead of 3 at the root
add convertion from SubsMat to Matrix for protein submatrix
BitString and strict_consensus
reorganize different tests
add automatic test for consensus tree
add `repr` funcionn for Matrix class and improve the document
move `delitem` and `insert` from DistanceMatrix to Matrix
fix the index bug of Matrix.insert() function and improve the document
test files for consensus algorithms
improve document of DiscanceCalculator and DistanceTreeConstructor
improve document for parsimony tree classes
majority and adam consensus methods
fix majority bug, finish adam consensus, doc improvement