specify bazel version for bazelisk (#627)

[Bazelisk](https://github.com/bazelbuild/bazelisk) is a wrapper for Bazel written in Go. It automatically picks a good version of Bazel given your current working directory, downloads it from the official server (if required) and then transparently passes through all command-line arguments to the real Bazel binary. You can call it just like you would call Bazel.
Signed-off-by: NHuahang Liu (Hans) <hliu@me.com>
Co-authored-by: NHuahang Liu (Hans) <hliu@me.com>

.bazelversion

+0.13.0
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