Update deface to display login nav bar on backend

admin layout in spree/spree was broke into partials in
https://github.com/spree/spree/commit/032fea840560d67838ad7f8c300be44994027893

Fixes #112
Bump capybara to ~> 2.1

spree/spree master now has capybara configuration that require that
version
Add color config.