Allow multiple orders to be accessed in succession in one session

Fixes #132

Conflicts:
	Gemfile

Conflicts:
	spec/controllers/spree/orders_controller_spec.rb
Revert "Bump to Devise 3.1.0"

This reverts commit dfb2b18e29b99dc406409b76ce1392360276fb9f.
Merge branch '2-1-stable' of https://github.com/radar/spree_auth_devise into 2-1-stable