chore(sbt): Bump to sbt 1.2.8

yoshinorin · yoshinorin · commit 2ef310845e2d · 2019-03-23T00:17:35.000+09:00
diff --git a/project/build.properties b/project/build.properties
@@ -1 +1 @@
-sbt.version = 1.2.6
+sbt.version = 1.2.8
