* Added drop_last to DeepSpeedDataLoader

This solves issue #326

* Updated drop_last in engine.py

added drop_last as a ds_config as mentioned by @tjruwase

* Update engine.py

* Update engine.py

* updated config.py and constants.py

* Update constants.py

* added dataloader_ prefix

* Update dataloader.py

* corrected yapf test errors

* Update test_data.py

Added dataloader_drop_last unit test

* Corrected yapf and formatting issues

* updated simple_model.py and test_data.py

* Update simple_model.py

* pre-commit fix

* corrected issues

* Update test_data.py

* Update test_data.py

* Update test_data.py

* Update test_data.py

* removed batch_size from test_data.py

* Update simple_model.py

* Update test_data.py

* Update test_data.py

* Fix unit test issues

* Use fp32 to make things work
Co-authored-by: NOlatunji Ruwase <olruwase@microsoft.com>
Co-authored-by: NJeff Rasley <jerasley@microsoft.com>