Switch required bazel version to 0.29.1

Based on the corresponding core change series started with Ib48fdbb6.

Change-Id: I9d2e3d32e426eaa4d4c768bb2dbdd76ae97e1bcc

.bazelversion

diff --git a/.bazelversion b/.bazelversion
index 8862dba..25939d3 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-1.0.0rc2
+0.29.1