Modified Disease Prediction jupyter notebook and added disease_prediction.py

[ankitkumarsamota121]

Modified the disease_prediction jupyter notebook and added the disease_prediction.py file under models folder in web_app. disease_prediction.py file contains following three functions:

• get_disease: Takes in a chemical name of a drug as a string and returns a list of all probable disease.
• get_chemical: Takes a common name of a drug and returns its chemical name.
• disease_from_tweet: Takes a tweet or any other string and returns a list of all probable diseases related to that tweet.