.travis.yml: Use Bazel 1.0.0
.travis.yml: Use Bazel 1.0.0

My update to rules_docker seems to need Bazel >= 0.29.1. With 0.28.1
the following error occurred on TravisCI. Since Bazel 1.0.0 has been
released, use that.

Fixes:

in platform rule @io_bazel_rules_docker//platforms:local_container_platform:
target '@local_config_platform//:host' is not visible from target
'@io_bazel_rules_docker//platforms:local_container_platform'. Check the
visibility declaration of the former target if you think the dependency is
legitimate

istio/distroless,GoogleContainerTools/distroless,GoogleContainerTools/distroless,istio/distroless,istio/distroless,GoogleContainerTools/distroless