API: removed math, skbio.math.$ -> skbio.$
TST: corrected import path for test_subsample.py
TST: moved test_subsample.py as nose ignores any subpackage with an `_`
API: made ordination.utils private
MAINT: pep8
MAINT: pep8
Merge pull request #561 from ebolyen/issue541

API: removed math, skbio.math.$ -> skbio.$
Merge branch 'master' into issue-523

Conflicts:
	CHANGELOG.md