update deps, fix linting, add nodes to testing matrix; migrate tests to github actions

[duoertai]

@csharplus

[ljharb]

What’s the point of this?

[ljharb]

Migrated to github actions, latest results are here: https://github.com/duoertai/hypernova/actions

@lencioni can you remove travis-ci from the required branch protections? then i can land this, and after that, we can make the actions status checks required.

[ljharb]

Thanks! Once the first three jobs on https://github.com/airbnb/hypernova/actions are completed, they can be added as required checks.

[lencioni]

I think we actually need 4 here. Does this look right to you?

[ljharb]

It's missing pretest and posttest, but otherwise yep!

[lencioni]

pretest and posttest are now added. thanks!