Migrate to non-deprecated constructor of CompileSetup.

The sbt/sbt#1122 and sbt/sbt#1125 introduced additional argument
(nameHashing flag) to CompileSetup and deprecated the old constructor.
Let's catch up with this change in zinc now.
Merge pull request #45 from gkossakowski/compile-setup

Migrate to non-deprecated constructor of CompileSetup.