Bump SemVer to 2.1.0-dev

Change-Id: I1b79ae34912827db03b3fc37c642da981dda6067
diff --git a/VERSION b/VERSION
index 227cea2..c10edc3 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.0.0
+2.1.0-dev