Switch the Gemfile source from `https` to `http`.

This is less than desirable and against Bundler's best practices, but:

- Many users will be behind firewalls that crack https connections.

- The build environment won't have the necessary certificates to make
  this work unless the developer locates and adds site-specific
  certificates to the Cygwin installation.

- `gem install` detects this and fails.

- `bundle install` doesn't detect the `gem install` failure and
  allows an incomplete build to continue.