Fix #1072: Bump sbt version to 0.13.5

Also see #1008, #1038.

This re-does eede37cc4fb87db96eae28a9a536c507233f1dd1 and
8f2169a37e77bca4cee8300c638e15d9eca138aa which were
reverted in 353e9635a2276e48b6ea6541e49f6c7ab8763b71.
And we were savagely blaming sbt for our mistake. How shameful of us...