Issue with pushing to Heroku

[fangyiyu]

Hi, thank you for providing this resource. I downloaded your git repo and tried to deploy it on Heroku, but it failed and the building log says "Failed building wheel for pandas", it seems Heroku cannot find pandas from the requirements.txt. Furthermore, I also encountered an Error: "Trying to unpickle estimator TfidfTransformer from version 0.22.2.post1 when using version 0.23.1. This might lead to breaking code or invalid results. Use at your own risk." Though the application can run locally, it can't run on Heroku due to the two issues I mentioned. I wonder if you met these issues when you deploy the app? and what are the solutions? I cannot find any useful ones on StackOverflow.