message: docs: update bazel README to include virtualenv
  Using buildifier failed without virtualenv so noting in the bazel README file. Also did some cleanup of the ordered list to always use "1.", see
  Risk Level: Low
diff: @@ -27,7 +27,7 @@ up-to-date with the latest security patches. See
  for how to update or override dependencies.
  1. Install the latest version of [Bazel](https://bazel.build/versions/master/docs/install.html) in your environment.
  -2. Install external dependencies libtool, cmake, ninja, realpath and curl libraries separately.
  +1. Install external dependencies libtool, cmake, ninja, realpath and curl libraries separately.
  On Ubuntu, run the following command:
  ```
  sudo apt-get install \
  @@ -38,7 +38,8 @@ sudo apt-get install \
  make \
  ninja-build \
  curl \
  - unzip
  + unzip \
  + virtualenv
  ```
  On Fedora (maybe also other red hat distros), run the following:
  @@ -66,10 +67,11 @@ build --action_env=PATH="/usr/local/bin:/opt/local/bin:/usr/bin:/bin"
  Alternatively, you can pass `--action_env` on the command line when running
  `bazel build`/`bazel test`.
  -3. Install Golang on your machine. This is required as part of building [BoringSSL](https://boringssl.googlesource.com/boringssl/+/HEAD/BUILDING.md)
  +1. Install Golang on your machine. This is required as part of building [BoringSSL](https://boringssl.googlesource.com/boringssl/+/HEAD/BUILDING.md)
  and also for [Buildifer](https://github.com/bazelbuild/buildtools) which is used for formatting bazel BUILD files.
  -4. `go get github.com/bazelbuild/buildtools/buildifier` to install buildifier
  -5. `bazel build //source/exe:envoy-static` from the Envoy source directory.
  +1. `go get -u github.com/bazelbuild/buildtools/buildifier` to install buildifier. You may need to set `BUILDIFIER_BIN` to `$GOPATH/bin/buildifier`
  + in your shell for buildifier to work.
  +1. `bazel build //source/exe:envoy-static` from the Envoy source directory.
  ## Building Bazel with the CI Docker image
  