Update to TensorIO 0.6.x and react-native-tensorio 0.3.0

• Small improvements and updates to our underlying machine learning interface

Most importantly:

• Use the new .tiobundle extension for model folders instead of .tfbundle
• Add a "backend" field to the model object in model.json, set to "tflite" or "tensorflow". See the example model included in this repo

Initial release with TensorIO 0.5.0

Merge pull request #5 from doc-ai/tensorio-update

Tensorio update