Update bcrypt-ruby Version in Gemfile Template

When using the current version of rails-api for a project, I came across a strange error with bcrypt-ruby.  By default, the Gemfile template included version **3.0.0**.  The rails/rails master branch has updated to bcrypt-ruby version 3.1.2, so I did the same for rails-api.  This error is now gone when someone uses the version specified in the template Gemfile:


> You don't have bcrypt-ruby installed in your application. Please add it to your Gemfile and run bundle install
Completed 500 Internal Server Error in 2ms