Merge branch 'stable-3.0'

* stable-3.0:
  Bump required Bazel version to 2.1.0

Change-Id: I8860de9b8a343f23f135c8d938add7fcf0420c11

.bazelversion

diff --git a/.bazelversion b/.bazelversion
index 227cea2..7ec1d6d 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-2.0.0
+2.1.0