Adding sorting code
Initial gradient classes with tests
Merge branch 'master' of https://github.com/biocore/bipy into gradient
Merge branch 'master' of https://github.com/biocore/bipy into gradient
Partially adding functionality
Stubbing tests
Adding pandas to setup
Add make_groups functionality
Merge upstream master
Adding tests for make_groups
Adding some tests
Adding tests for normalize_samples
Adding tests for make_groups
Adding tests for weight_by_vector
Added descending branchlength method

Method allows calculation of descending branchlength in trees and replaces the cogent functionality totalDescendingBranchlength().
Added tests and resolved some pep8 problems
Updated tests and pep8 compliance
Final pep8 checks out
Pep8...
Resolve documentation error.