Define AttributeBase

Per SAML 2 Metadata spec.
Prevent FactoryGirl from breaking migrations
Test all FactoryGirl factories and traits

Ensure that potential future model changes are correctly reflected in factories which are used in subsequent specs.

Enable Guard to run specs when factory files are modified.
Define Attribute

Per SAML 2 Metadata spec.
Link AttributeValue to owning Attribute
Refine schema for Attribute and related models
Define RequestedAttribute

Per SAML 2 Metadata spec.