Make screenshot-uploads bucket public for read

[gugu]

There is nothing secret (I think) in this folder

If all files there will be public, I can update npm run test:image-diff and travis.yml file to download files from this bucket using public URL if there is no MDC_GCLOUD_SERVICE_ACCOUNT_KEY present.

It will make tests for pull requests to be green if no golden files changed. And as soon as maintainer uploads the new golden - pull requests will become green as well

For the repository tests will run as usual because it has MDC_GCLOUD_SERVICE_ACCOUNT_KEY set for travis

[moog16]

@gugu can you try now? https://console.cloud.google.com/storage/browser/screenshot-uploads

[gugu]

Thanks. Created #638

[moog16]

closing. looks like it is working..this saves a ton of time!

[moog16]

Sorry - I jumped the gun on closing this. I'll review #638

[gugu]

Thanks