pzmm.JSONFiles.calculate_model_statistics generate wrong files

[ryanma9629]

pzmm.JSONFiles.calculate_model_statistics should generate a fit stat file, a roc file, and a lift file. However, it generates three fitstat files with different names but the same contents. This can be reproduced by the examples/pzmm_binary_classification_model_import.ipynb

[smlindauer]

Thanks @ryanma9629. It looks like the json dump at the end of the SWAT calls was properly implemented for only the dict return case. Adding a fix momentarily.