bump sbt version

SethTisue · SethTisue · commit c8adeae83fa9 · 2019-01-08T19:38:28.000-08:00
no special reason, just keeping current
diff --git a/project/build.properties b/project/build.properties
@@ -1 +1 @@
-sbt.version=0.13.17
+sbt.version=0.13.18
