update project setup to make collaboration easier

[Goldziher]

Hi There,

So i forked this repo to make some updates and I encountered some difficulties with the setup- I would like to suggest the following updates:

1. migrate to using poetry instead of setup.py, and then add the dependencies and dev dependencies at the root level.
2. migrate to using github actions, works with poetry: https://github.com/snok/install-poetry
3. add pre-commit
4. add contribution guidelines
5. add unit tests - currently there is really nothing

I would be glad to help with some of these if you are interested.

[timthelion]

Would 1 maybe fix #20 ?

[timthelion]

What would be in 3?

[timthelion]

5 the only "test" is this

django-import-export-celery/example/winners/tests/test_admin.py

Line 9 in 67b9fa6

class AdminSmokeTest(tests.AdminSiteSmokeTest):

[timthelion]

What would 2 do?

[timthelion]

You did see that we have travis https://travis-ci.com/github/auto-mat/django-import-export-celery/jobs/506689595 didn't you?

[Goldziher]

So,

1.poetry is very nice and simple to use.
2. See this for pre-commit: https://link.medium.com/HVz8neQ5pgb
3. Travis changed their policies, and github actions are great.
4. Zero coverage

[timthelion]

How did travis change their policies?

[Goldziher]

Well, they changed their policy regard open source etc. Google it.

Anyhow, I ended up writing custom logic instead of using this library.