Use 'https://rubygems.org' instead of :rubygems

Avoids deprecation warning and is more secure.
Remove unused 'formtastic' gem
Use the same Gem versions as we've packaged

So we use the exact same versions in development and in the product.
We'll need a better way to handle this though rather than relying on
manual updates.
Add bootstrap, as requested by Ken

Rails 2 doesn't have Sprockets like in Rails 3, so we need to include
Compass in order for bootstrap-sass to work.

We'll need to package rubygem-bootstrap-sass and rubygem-compass-rails
accordingly as RPMs and add it to the ISO.