kit.pairwise tests

[untzag]

add tests for kit.pairwise

[ksunden]

This is fairly easy to test, though it is directly copied from the python.org docs, but may as well explicity test. We also get coverage/usage tests from split

[untzag]

yep---this issue is not blocking for anything whatsoever

would be a good first project for someone interested in learning how to write unit tests