add 2nd requirements to distinguish for gpu and non-gpu supported platforms

requirements.txt

@@ -54,7 +54,7 @@ six==1.11.0
 statsmodels==0.11.1
 tensorboard==1.13.1
 tensorflow-estimator==1.13.0
-tensorflow-gpu==1.13.1
+tensorflow==1.13.1
 termcolor==1.1.0
 toolz==0.10.0
 urllib3==1.25.8

requirements_gpu.txt

+absl-py==0.9.0
+astor==0.8.1
+atomicwrites==1.3.0
+attrs==19.3.0
+Cartopy==0.17.0
+certifi==2019.11.28
+chardet==3.0.4
+cloudpickle==1.3.0
+coverage==5.0.3
+cycler==0.10.0
+Cython==0.29.15
+dask==2.11.0
+fsspec==0.6.2
+gast==0.3.3
+grpcio==1.27.2
+h5py==2.10.0
+idna==2.8
+importlib-metadata==1.5.0
+Keras==2.2.4
+Keras-Applications==1.0.8
+Keras-Preprocessing==1.1.0
+kiwisolver==1.1.0
+locket==0.2.0
+Markdown==3.2.1
+matplotlib==3.2.0
+mock==4.0.1
+more-itertools==8.2.0
+numpy==1.18.1
+packaging==20.3
+pandas==1.0.1
+partd==1.1.0
+patsy==0.5.1
+Pillow==7.0.0
+pluggy==0.13.1
+protobuf==3.11.3
+py==1.8.1
+pydot==1.4.1
+pyparsing==2.4.6
+pyproj==2.5.0
+pyshp==2.1.0
+pytest==5.3.5
+pytest-cov==2.8.1
+pytest-html==2.0.1
+pytest-lazy-fixture==0.6.3
+pytest-metadata==1.8.0
+python-dateutil==2.8.1
+pytz==2019.3
+PyYAML==5.3
+requests==2.23.0
+scipy==1.4.1
+seaborn==0.10.0
+--no-binary shapely Shapely==1.7.0
+six==1.11.0
+statsmodels==0.11.1
+tensorboard==1.13.1
+tensorflow-estimator==1.13.0
+tensorflow-gpu==1.13.1
+termcolor==1.1.0
+toolz==0.10.0
+urllib3==1.25.8
+wcwidth==0.1.8
+Werkzeug==1.0.0
+xarray==0.15.0
+zipp==3.1.0