[wip] add hypothesis tests of transformer

[nrbgt]

• add hypothesis and pytest plus some additional bits and bobs
  • anaconda-project.yml
  • setup.cfg
  • anaconda-project-lock.yml
    • brought in a fair amount of new stuff, will be interesting to see...
• add test infra in dodo
  • needs pyflakes to have run
  • needed by all
• add basic test setup (in-tree)
  • we don't have to ship the tests, but....
• create some hypothesis strategies for valid inputs to XELK

[nrbgt]

Given the above links to #23, #29, let's cool on this work until we have a better oracle for determining whether the inputs are sound, and not just "enters deadlock", which is what i was hoping to suss out...