Change Deserializers to support value types

Fixes #564
Merge branch 'master' of git://github.com/darvids0n/RestSharp into darvids0n-master

Conflicts:
	RestSharp/Deserializers/JsonDeserializer.cs
	RestSharp/Deserializers/XmlDeserializer.cs
Added a test for deserializing JSON into a struct
Added a test to deserialize xml into a struct
Merge branch 'darvids0n-master'