Update tutorials

[Karim-53]

Elsalem,

Guys I have spent one day trying to run the first ML model unsuccessfully.
Problem is, there are different tutorials across the repo:

• README.md propose to run the following

download.py: Download the Tarteel dataset
create_train_test_split.py: Create train/test/validation split csv files.
generate_alphabet|vocabulary.py: Generate all unique letters/ayahs in the Quran in a text file.
generate_csv_deepspeech.py: Create a CSV file for training with DeepSpeech.

But I am stuck at generate_csv_deepspeech.py
And I don't know what is the purpose of each data generated...

• The wiki refer to py files that have been deleted long ago

Navigate into the audio_preprocessing directory and run python generate_features.py

• wiki and CONTRIBUTING.md both explains how to set up the repo. It is just redundant...

I suggest that

1. we update README.md with the minimum instruction to run the simplest ML model. and I would need your help with that please please
2. we keep using CONTRIBUTING.md to explain how to set up the repo and bring the related content from the wiki here coz contributors can modify README.md easily but not the wiki as explained here How to Add/Edit Wiki pages? #51