index.md: Suggest "pip install -U" to upgrade to the latest version

Bare "pip install" won't update to a newer version if a packages is already
installed.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: Id7b6211442fe50425a1e22a4bae7c723c6ffcc44
1 file changed
tree: cf120428945644cff1e17cb2c6df241f1e8c0730
  1. docs/
  2. .gitreview
  3. mkdocs.yml
  4. requirements.txt