restore tests passing in CI

[staltz]

• Replaces Travis with GitHub Actions
• Targets Node.js 12.x, 14.x, 16.x in tests (these are versions of Node.js currently actively maintained)
• Uses tap-spec to make tests print out more pleasantly
• Introduces npm run test-verbose to run the old-style console.log fest
• Some tests files were not tape, I made them become tape tests
• Pins ssb-friends to 4.3.0 which is an old version where we're sure tests with ssb-ebt still pass
  • This should change soon once https://github.com/ssbc/ssb-friends/pull/66 is merged and released

[staltz]

Otherwise looks good. Great to have this running proper CI.

Thanks for taking a look! Before merging I still want to make all 3 versions green, though. It's weird that CI always passes 2 but 1 stays red, and it's not always the same one.

[staltz]

All green!