I'm working my way through the Heroku workbook and have hit a roadblock early in the process. I have installed Ruby and the Heroku toolbelt and am trying to set up a Gemfile as documented in the workbook. 

I can run the $gem install bundler command, but when I try to execute the next step, $bundle install - I get the following error: 

Bundler: GemfileNotFound

Any suggestions? I have a file called Gemfile.rb in the workbook directory. What am I missing? 

Thanks,