Scan an assembly in order to create a DataContractContentSerializer

Resolves #100.
I started by adding [this](https://github.com/moodmosaic/AtomEventStore/commit/12d4a71c94b5499ddd0f9f92d974cb533d9c20dc) commit and then I added [this](https://github.com/moodmosaic/AtomEventStore/commit/003c6f87a4076918bdefbcf1aa7937068596ef52), in order to return the correct `IContentSerializer` result.