Arvados

See this ruby-talk message. Gem's install behavior is highly stateful, and our non-RVM Gem install instructions can go wrong in many different ways depending on that state. Permissions might be wrong for the installed gems because they respect root's umask; necessary gems might not be installed system-wide if they're already in root's ~/.gem; and spec files will not be installed system-wide.

Everywhere the Install Guide instructs users to install Gems without RVM, update the instructions to be robust against these issues to ensure all necessary gems will be installed so all users can use them.