Feature/update gems

Updates all gems to the latest versions, migrates RSpec to version 3. 

Not updated:
- Capistrano 2 (no migration planned yet)
- Foundation 3 (will be removed with the redesign)
- Rails 3 (migration is separate feature https://github.com/teikei/teikei/issues/2)
- Jasmine 1 (can't get version 2 running with backbone/marionette yet)