Fix issue where generated js is equal to html file

Hey @nicklink483,

I had a problem yesterday where the JS file generated had the same content as the HTML file, and I saw a report of this on /r/ruby earlier. The problem for me was that when running `rake build`, the `bundle show dare` command was throwing an error because I hadn't run `bundle install`, but when I tried to `bundle install`, the source was missing. 

This adds the source and edits the README in order for users to run `bundle install` after generating a new game. Also deletes the apparently unused `bin/dare.rb` which looks like an outdated version of `bin/dare`. 

Please check it out!