* Add venv and .venv to gitignore since common venv paths
* Update cookbook-plain app requirements and local-dev notes
This also adds the DEFAULT_AUTO_FIELD to the app's Django settings to
resolve this warning when running `migrate`:
```
ingredients.Category: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
HINT: Configure the DEFAULT_AUTO_FIELD setting or the IngredientsConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.
```
* Fix#1417 graphiql explorer styles by including official CSS
Like in the official graphiql-plugin-explorer example here
6198646919/packages/graphiql-plugin-explorer/examples/index.html (L26-L29)
Resolves https://github.com/graphql-python/graphene-django/issues/1417
* Update GraphiQL version
---------
Co-authored-by: Steven DeMartini <sjdemartini@users.noreply.github.com>
Co-authored-by: Kien Dang <mail@kien.ai>
* Update travis and tox
* Use xenial distribution
* Don't install coveralls twice
* Add black and flake8 tox commands
* Remove Python 3.5 test for Django master
* Fix indent
* Ignore migrations
* Remove black for now
* Run black formatting (#668)
* Run black format
* Update makefile
* Add black to travis build
