Bump Bazel version to 3.0.0

Change-Id: If0593de321c3f44455e199fa30db11a2fb791fd0
diff --git a/.bazelversion b/.bazelversion
index ccbccc3..4a36342 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-2.2.0
+3.0.0