Please create requirements.txt for easy package installation

The package setup can be made easier with package instalation via `pip install -r requirements.txt` ([read more](https://pip.pypa.io/en/latest/user_guide/#requirements-files)).

Some packages are not straightforward, for example:

+ `opencv-python` is the package name for when you need to `import cv2` ([details](https://github.com/jazzsaxmafia/video_to_sequence/issues/3#issuecomment-277377381))

+ without [Pillow](https://github.com/python-pillow/Pillow), the code runs without import error, but you get the following runtime error `AttributeError: module 'scipy.misc' has no attribute 'imresize'` ([details](https://stackoverflow.com/a/15345969/2327328))

To create:

pip freeze > requirements.txt

and here's mine, with python3.7 in a virtual environment:

[requirements.txt](https://github.com/carpedm20/DCGAN-tensorflow/files/3124014/requirements.txt)

```
absl-py==0.7.1
astor==0.7.1
gast==0.2.2
grpcio==1.20.1
h5py==2.9.0
Keras-Applications==1.0.7
Keras-Preprocessing==1.0.9
Markdown==3.1
mock==2.0.0
numpy==1.16.3
opencv-python==4.1.0.25
pbr==5.2.0
Pillow==6.0.0
protobuf==3.7.1
scipy==1.2.1
six==1.12.0
tensorboard==1.13.1
tensorflow==1.13.1
tensorflow-estimator==1.13.0
termcolor==1.1.0
Werkzeug==0.15.2
```