Hail 118

[illusional]

Stacks on: https://github.com/populationgenomics/hail/pull/298

[jmarshall]

There may be alternative approaches in Git to carry our local changes on top of upstream's vendor branch more clearly and with perhaps less work — e.g. I tend to prefer a local branch of additions that gets rebased periodically —, but that is a conversation for another day.