Document how to use Pry

Closes https://gitlab.com/gitlab-org/gitlab-development-kit/issues/140

Added 1 commit:

• c65d0044 - Document how to use Pry

Status changed to merged

mentioned in commit e3693499

Hey thanks @jacobvosmaer-gitlab , in my case I also had to add these into the Gemfile:

group :development, :test do
  gem 'pry'
  gem 'rb-readline'
end