$ mkdir myapp
$ cd myapp
$ echo "source 'https://rubygems.org'" > Gemfile
$ echo "gem 'rails', '5.0.0.1'" >> Gemfile
$ bundle install

bundle exec rails new 

bundle exec rails new . --webpack=vue --database=postgresql --force

Ref: https://stackoverflow.com/questions/379141/specifying-rails-version-to-use-when-creating-a-new-application