https://*.com/questions/12200215/bunder-what-does-require-nil-in-gemfile-mean
Require nil or false means that bundler will not load (require) the specific gems. However, they will be in the $: load paths, so you can require them explicitly any time you want to use them. It is a good practice to use this, for gems that are only needed in special cases (e.g. external scripts, rake tasks etc.).