Add tests for R-to-JSON serialization.
Add tests for R-to-JSON serialization.

AlexanderSher/RTVS,karthiknadig/RTVS,MikhailArkhipov/RTVS,AlexanderSher/RTVS,karthiknadig/RTVS,MikhailArkhipov/RTVS,AlexanderSher/RTVS,AlexanderSher/RTVS,MikhailArkhipov/RTVS,MikhailArkhipov/RTVS,karthiknadig/RTVS,karthiknadig/RTVS,karthiknadig/RTVS,AlexanderSher/RTVS,karthiknadig/RTVS,MikhailArkhipov/RTVS,AlexanderSher/RTVS,MikhailArkhipov/RTVS,MikhailArkhipov/RTVS,karthiknadig/RTVS,AlexanderSher/RTVS