Added the ServiceName element.
Moved the Attribute element into an AttributeType ComplexType, since both the Attribute element as well as the RequestedAttribute are going to use it.
Added the ServiceDescription element.
Added the RequestedAttribute element, which includes the complex type AttributeType.
Added the AttributeConsumingService element.
Added the AttributeConsumingServices to the SP SSO descriptor element.
Merge pull request #8 from digidentity/attribute-consuming-service

Added the AttributeConsumingService and it's subelements.

Nicely done!