Use rspec-rails public api to set engine route set

rspec-rails guys helped to figure this out so no need to override
private api anymore
Point to just created rails/4-2-stable branch
Merge branch 'master' into rails-4-2

Conflicts:
	api/config/routes.rb
	core/lib/spree/core.rb
	core/spree_core.gemspec
Merge remote-tracking branch 'upstream/rails-4-2' into rails-4-2

Conflicts:
	api/config/routes.rb
	common_spree_dependencies.rb
	core/spree_core.gemspec
Use `paranoia_destroyed?` for soft delete check

This is not default api, maybe yet, in paranoia but should keep builds
green for now
point to rails/4-2-0