Introduced XmlContentSerializer.Scan.
Implemented XmlContentSerializer.Scan.
Added a test case.
Documented XmlContentSerializer.Scan.
Incremented minor version,

in order to indicate that the addition of the Scan convenience method to
the XmlContentSerializer class is a new feature.

This resolves #101
(https://github.com/GreanTech/AtomEventStore/issues/101).