switch to pipfile, add pylint & black

[jstriebel]

This PR adds some project setup:

• Python 3.7 is recommended, installation via pyenv is described in README.
• Adds Pipfile for pipenv.
  • Instructions are in README.
  • Dockerfile is adapted.
• Adds pylint and black (code-formatter).
• Code is formatted.

[hotzenklotz]

Regarding Python 3.7: IIRC, our other libs (wkw, wkcuber, seg-tools) all run on Py 3.6 for compatibility. Some dependencies are not available for Py 3.7 yet. Perhaps @georgwiese or @philippotto can comment on that.

[georgwiese]

segmentation-tools are still using Python 3.5, because that's what's shipped with the official TF image.

[jstriebel]

I just checked the versions:

• wkw is built with 3.6 and checked against 3.4 and 3.5 as well. We could and should test against 3.7 as well, see https://github.com/scalableminds/webknossos-wrap/pull/28
• wk-cuber specifies only the docker image python:3 which is currently 3.7.2. Probably we should fix the minor version here, see https://github.com/scalableminds/webknossos-cuber/pull/53
• segmentation-tools is at 3.5, as @georgwiese explained.

I'm fine with using Python 3.6 as well, 3.5 is missing important features for typing. As py-datastore will not be used by one of those libs, having a higher version should not be an issue, so I would go for the most recent, but 3.6 is also fine for me. Using the libs should not be a problem anyways, as the versions are downward-compatible.

CCing @normanrz , as he seemed to setup most of the other python projects.

[normanrz]

If all the deps are compatible with 3.7, I don‘t see why we shouldn’t use ot for this project. Eventually, TF will also support it and we can also migrate segm-tools.

[normanrz]

I think it is convention to not use dashes in module names on Python, or is it?

[jstriebel]

I think it is convention to not use dashes in module names on Python, or is it?

It is, I'm changing it in PR #9