Add specs for a subscriber that is not a user
Add implementation of a subscriber, it allows us to subscribe people which are not users in our system
Refactor Subscriber class to use more conventional methods from ActiveModel.

This has certain benefits:

*  Easier to create forms
*  Allot of validation for free
*  Allows validating of email to not be blank
*  Adds mass-assignment protection.
Merge branch 'master' of https://github.com/DynamoMTL/spree-hominid into subscribers
Convert activemodel to AR Model
Switch to Spree::Chimpy::Subscriber, to match the new name
Quite a lot of changes included:

*  Add segmentation to the interface
*  Automatically segment all users, but don't segmentize subscribers
*  Add a preference for adding the ID of a segment
Merge branch 'master' of https://github.com/DynamoMTL/spree_chimpy into subscribers

Conflicts:
	lib/spree/hominid/subscription.rb
	spec/lib/configuration_spec.rb
Update after the rename to spree_chimpy
Merge branch 'master' of https://github.com/DynamoMTL/spree_chimpy into subscribers
Add a route + controller for taking subscriptions
Add a sign-up form with a default override
Add i18n for NL & EN
Use a HTML5 input type=email to be more mobile friendly.
Namespace i18n
Merge branch 'master' of https://github.com/DynamoMTL/spree_chimpy
Fix segment_emails call
Minor documentation fixes
Adds pry to gemfile
Fixes whitespace