Fix unit test name in pairwise tests
Remove duplicated warnings.simplefilter calls

...in favor of setUp/tearDown methods.
Add assert_warns call to Alignment.toFasta test
Add assert_warns calls to beta-diversity tests
DOC: Add doctest for pwmantel
DOC: add additional doctest examples to pwmantel

Showing/describing usage of ``lookup`` and ``strict``.
Merge pull request #615 from jairideout/issue-479

Remove duplicate code in unit tests used to ignore warnings
Move dm-matching code into mantel

Previously was in pwmantel, but it makes sense to support matching of distance matrices in both functions. Minimal updates to tests and docs to get things passing again. Still need additional changes to unit tests, doctests, and documentation.
Move shared test data into base class

Prepping for refactoring of unit tests.
Add unit test class for _order_dms

This function is more complicated now so it makes sense to explicitly test it.
Add error-path tests for _order_dms
Remove duplicate test data in MantelTestData
Add _order_dms tests for reordered/mismatched dms
Change call to list(dict.keys())

I just thought it looked strange, so I'm proposing this minor edit.
Add remaining unit test for _order_dms (testing id lookup)
Add checking of n value being returned by mantel
Add reordering/nonmatching/lookup tests for mantel function
pwmantel now accepts array_like as input
update docstrings/doctests for mantel and pwmantel
Fix doctest, pep8, and flake8 errors