ENH: checklist.py now enforces a minimal API in tests
MAINT: Unneeded else clause, no longer prefers alternate import if not any deeper
MAINT: Code cleanup for APIRegressionValidator
TST: all tests use minimum API
MAINT: corrections to checklist.py
DOC: explanation of minimally deep api imports in tests
DOC: explanation of minimally deep api imports in tests
Merge branch 'EnforceAPI' of https://github.com/ebolyen/scikit-bio into EnforceAPI

Conflicts:
	doc/source/development/coding_guidelines.rst
Merge pull request #543 from ebolyen/EnforceAPI

ENH: checklist.py now enforces a minimal API in tests