chore: update React peer dependency to ^16.8.0 (alternative)

[trojanowski]

BREAKING CHANGE: minimum supported (and tested) version of React is now 16.8.0

Closes #71

[avocadowastaken]

TBH I don't really know what benefits we get from act (as far as I know we will need it for seamless transaction from class components to functional with hooks without breaking the test). So I guess shutting it down is ok. But on the other hand - wouldn't it be easier just to shut down console.errors with act messages ? :)

[trojanowski]

wouldn't it be easier just to shut down console.errors with act messages

I guess that using act can be helpful in some cases. We identified one place where it's not enough to get rid of warning messages. I think that maybe in the future those warnings can help us to identify some bugs, so it's a bad idea to silence them all.