* Newtonsoft dependency updated.
* Fixes JSON.NET serialziation issue with ButtonStyle and ButtonType enum types in ButtonRequest. DefaultValueHandling serialization behavior changed in Newtonsoft that caused unit test to fail.

Setting a non-zero value that is not default(int) corrects JSON.NET serialization output when DefaultValueHandleing.Ignore should not have any effect since int values are not used in coinbase's API.