ENH: update to remove cogent dependency, fixes #1552
first pass as porting to use skbio's majority_rule
ENH: updated scikit-bio dependency version
Merge branch 'issue-1552' into issue-1551
Merge pull request #1618 from gregcaporaso/issue-1552

remove cogent neighbor joining dependency in favor of skbio
Merge pull request #1619 from gregcaporaso/issue-1551

porting to use skbio's majority_rule
added suma
Merge branch 'new-software-otu-picking' of https://github.com/ekopylova/qiime into new-software-otu-picking

pulled API updates
tests finished for pick_open_reference_otus using sortmerna and sumaclust, sortmerna_otu_id_prefix option removed - now reference sequence ID is the OTU id to be consistent with other methods
pep8
Merge branch 'master' of https://github.com/biocore/qiime into new-software-otu-picking

pull changes from upstream