Don't ignore Gemfile, needed to load dev/test dependencies via bundler
Update gitignore app for changed dev/test env:

- spec/test_dir is now called spec/dummy
- don't track .bundle
- don't track vendor/bundler
Add Gemfile and Gemfile.lock
Add development dependencies to gemspec file
Require spree/auth/devise and spree/authentication_helpers is main lib
file
Namespace spree classes under Spree:: in model specs
Require dummy environment and should matchers in spec_helper