Closes #29 - Added _tail tag tests
Added "pending" test to .wait()
Re #20 - Added unit tests for Flow namespace
Fixed _on tag and (re #20) added unit tests
Polished _on tests
Re #20 - revised unit tests for traversal tags: _on, _in, _out, _over, and _bover.
Patched issue where shorthand _on queries resolved to the same state