Update Kubernetes to 1.10 (still supported by EKS until end of July)
Update Helm to 2.12 (this is the version we have switched to ourselves,
to avoid bugs in older versions)

I also updated the default EKS version in our eks boostrap script to be
1.11 rather than 1.10. Even though EKS supports 1.10, Kubernetes
upstream does not, so we shouldn't be using it by default at all.