Bump jest to 24.8.0

[Tbaut]

Self explanatory, and more sensible this time :)
Tested successfully the build and functionnalities on android.

[pmespresso]

it looks like there's two lock files. I think it's generally best practice to choose one or the other (yarn or npm) to avoid inconsistencies.

[Tbaut]

Do you mean I should remove the yarn.lock? I've had the package-lock.json in previous PRs`

[pmespresso]

As long as it's consistent it should be no problem. Dug a little into past PR's where just the yarn.lock is committed. e.g. https://github.com/paritytech/parity-signer/pull/232/files

[maciejhirsz]

I don't have any strong feelings for or against yarn/npm, so adding whichever lock file on .gitignore and then using the other is fine with me. npm might be a bit easier since we can then remove yarn from required dependencies for the setup, but I reckon it isn't really a blocker for anyone.

[pmespresso]

LGTM, @Tbaut could you please also add one of the lock files to gitignore in this PR? shouldn't really matter which one :)

[Tbaut]

I went for removing the yarn.lock and adding it to .gitignore,

[pmespresso]

ah I just realized the setup_macos.sh script actually runs yarn at the :/

I will change this to npm install in a separate PR

[lexfrl]

I went for removing the yarn.lock and adding it to .gitignore,

Consider to read this:
https://yarnpkg.com/blog/2018/06/04/yarn-import-package-lock/

We highly recommend you to delete the package-lock.json file if you decide to use yarn in order to avoid future confusion and possible consistency issues.