CI things

[CJ-Wright]

We most likely need go get off Travis, so we should figure out how to do that.

Current proposals include:

• use conda-forge's system
• github actions

@martindurant

[martindurant]

Ref: dask/community#107

[martindurant]

Looking for volunteers...
With any luck, changing the CI will also fix the kafka test that times out on travis (but passes locally).

[jrbourbeau]

Can this be closed? It looks like CI was migrated to GitHub actions in https://github.com/python-streamz/streamz/pull/402/files and Travis was removed in #403