Don't use --prefer-offline

If you set --prefer-offline to true in npm, naively thinking (like I did) that this will speed up your npm installs, you will be disappointed (like I was). Annoyingly, this setting causes npm to also cache which packages and versions don't exist. Thus, updating a dependency to a newly published version causes npm to think it doesn't exist and, instead of doing anything about it, npm will simply error out.