Support for deserializing dictionary with integer key

[mikaelharsjo]

When trying to deserialize my object containing the dictionary I get: Cannot deserialilze json into dictionary of type System.Int32. Dictionary key type must be string.

[jlarsson]

Fixed. In general, dictionary keys can be of any type, but if

System.Convert.ChangeType(<member name>,typeof(TKey))

fails, deserialization throws an informative exception.