google-java-format is not uniformly available in package management
systems across OSes. More importantly, we want to make sure that all
contributors are using a standardized version, to avoid unnecessary
changes due to slight differences between versions.
While we're in the dev documentation, link to the Google Java Style
Guide, and remove some wording that is clearly redundant with the style
guide.
Change-Id: Ib14dab2e692339f836083fad08a7a435a2f24470