Update to Jest 24

Created by: lorenzorapetti

Things to notice before merging

• There's currently a bug for which jest 24 crashes if it's called programmatically. Until a bugfix comes out, i've added require('jest-cli/build/cli') before require('jest') like this comment suggests. This has been fixed in version 24.1 🎉

• The current version of jest-pnp-resolver doesn't work because jest changed the file names of jest-resolve. They already have the fix in their code but it isn't published yet. I've filed an issue, but in the meantime i've created pnpResolver.js just to make things work. Fixed in jest-pnp-resolver 1.1.0 🎉

• Jest 24 comes with a new setupFilesAfterEnv option that replaces setupTestFrameworkScriptFile. It now accepts an array of files instead of a single one. I'm wondering if we should allow multiple setup files?