This has the benefit that: * Allows the installation of bundler as a default gem from rubygems to include man pages. * Removes the need to build man pages during our tests. * Makes working with the manifest easier, because we only have source controlled files, and not a mix of source control and generated files. To make sure they never fall out of sync, we replace the previous `man:build` CI task with a `man:check` task that makes sure the generated man pages are up to date. https://.com/bundler/bundler/commit/23de1d0177