title: You passed :github as an option for gem 'spree_gateway', but it is invalid
body: <p>When I try to install spree on a new app I get this error:</p>
  
  <p>You passed :github as an option for gem 'spree_gateway', but it is invalid.</p>
  
  <p>I am using rails 3.2.11 on windows 7 machine.</p>
  
  <pre><code>D:\Dropbox\web\rails_projects\testapp&gt;spree install
  Would you like to install the default gateways? (Recommended) (yes/no) [yes] y
  Would you like to install the default authentication system? (yes/no) [yes] y
  Would you like to run the migrations? (yes/no) [yes] y
  Would you like to load the seed data? (yes/no) [yes] y
  Would you like to load the sample data? (yes/no) [yes] y
       gemfile  spree
       gemfile  spree_gateway
       gemfile  spree_auth_devise
           run  bundle install from "."
  ←[31mYou passed :github as an option for gem 'spree_gateway', but it is invalid.←[0m
  </code></pre>