Bump Bazel version to 2.0.0

Change-Id: I09b36964b8f55dd43bdaf1b444c149793260fa2d

.bazelversion

diff --git a/.bazelversion b/.bazelversion
index 9084fa2..227cea2 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-1.1.0
+2.0.0