Exception when non default contract resolver is used

[mortenbock]

When serializing to Json, an exception is thrown if the default contract resolver is not used.

Code:

Newtonsoft.Json.JsonConvert.DefaultSettings = () => new JsonSerializerSettings{
	ContractResolver = new CamelCasePropertyNamesContractResolver()
};

Review r = new Review {
	Comment = "fdsdf"
};

r.ToIndentedJson().Dump();

Exception:
A member with the name 'comment' already exists on 'MXTires.Microdata.Review'. Use the JsonPropertyAttribute to specify another name.

The ToJson methods should specify the contract resolver explicitly to avoid this.