Bump Gerrit API to 2.15.1

Change-Id: I36e2ff9211e3220032e255d1c4851932a0304b95
diff --git a/build.sbt b/build.sbt
index 23def50..62635ef 100644
--- a/build.sbt
+++ b/build.sbt
@@ -6,7 +6,7 @@
 
 scalaVersion := "2.11.8"
 
-val gerritVersion = "2.15-SNAPSHOT"
+val gerritVersion = "2.15.1"
 
 val scalatraV = "2.4.+"