Several changes as a pull request

[agn-7]

Major changes:

• Add a Jupyter file in order to use it in Google-Colab or Jupyter-notebook.
• Remove a hard code target_Emotion from source code and use the configuration value instead.
• Retrain the entered word-embedding is disabled to speed up the training phase (it's not necessary to update and retrain a pre-trained word-embedding file).

Minor changes:

• Readme is updated
• Some refactoring and observer PEP8 convention.
• Change Tensorflow 2.0.0-beta0 to Tensorflow 2.0.0-beta1.
• requirements.txt is added in order to use in installation.

[agn-7]

What's wrong with this pull request that you've not accepted?