add support for campaign conversion for shop using api controller
creates a user into mailchimp when an order is sync
put additional test expectation for the auto create users for new orders
Merge pull request #35 from mickeyren/fix/api-compatibility

add support for campaign conversion for shop using api controller
lowered spree core version for lesser conflict
use the one from mail chimp or fall back to the orders email
Merge pull request #36 from mickeyren/fix/api-compatibility

lowered spree core version for less conflict