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
Remove skbio.app subpackage in favor of burrito.
Merge pull request #561 from ebolyen/issue541

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

Conflicts:
	CHANGELOG.md
Merge pull request #565 from jairideout/issue-523

Remove skbio.app subpackage in favor of burrito.
Move exception and warning module under skbio.util
Update imports to use skbio.util.exception/warning
Update docs to reference util.exception/warning
Add note to changelog
Merge pull request #569 from jairideout/issue-567

Move skbio.core.exception/warning to skbio.util.exception/warning