Use sbt 0.12.4, scrooge 3.1.5, cleanup build settings.

Squashed commit from master of the following for 2.4.1:

commit 5a7ff9d29996125ce019fc19c4549c450f0f5a2b
commit c52e838bf153bccba8ba6a0bae6b526188ad1a2c
commit 4b527763d01c1d79d0a932cecb19824aed2293a8
commit 4916f34076b44bff37b22ece1d13c07236866603
commit 8f825ac47b6b72ebbd9526a4d4a20698c66dca2d
commit 359d148cd69a0ba421b6a6c17bf1a945f083ef45
commit cf3c245aa57318bc5b13aebb5ccf7bcbb846416b
commit 975fd1cc736373f87aaede2fbbf4cc79d163b51b