Convert tensor dtype to float64

[christinaexyou]

When the .results or to_json() method is called on models bootstrapped using the SequenceClassification module it returns an error. For example:

MODEL_ID = "JungleLee/bert-toxic-comment-classification"
BOOTSTRAPPED_TOXICITY_CLASSIFIER = SequenceClassification.bootstrap(MODEL_ID)
classification_results = BOOTSTRAPPED_TOXICITY_CLASSIFIER.run(DOCUMENT)
print(classification_results.results)

Output:

TypeError: Object of type <class 'numpy.float32'> is not JSON serializable

This PR resolves this error by converting the tensor data type to float64 before converting it to a numpy array.

[evaline-ju]

LGTM - thanks!