people have more RAM in their machines these days, and more cores
too which means more parallelism which needs more heap. I've sometimes
seen sbt give GC warnings, so that's evidence more heap would help,
and 2G is still pretty small by current standards so I don't really
see a downside here
We've seen stack overflows on travis lately. Since we're using 1M on
Jenkins and didn't see failures, let's see if Xss1M fixes it on travis.
https://github.com/scala/scala-dev/issues/570