Shipment Mailer added.

Change-Id: I1bd6ae2af36ac2df3009e40c2c29340ed5367c32
Relationship between store and email templates.

Change-Id: I7bec89d87cf8af9b94d80569d94f9b23cde5b9be
Proper gemspec.

Change-Id: Iac77a76be1584cfb5b01021f32ba6416745717bb