Remove support and references to Heroku

Heroku will end their free tier.

README.md

@@ -7,12 +7,12 @@
 [![Language grade: JavaScript](https://img.shields.io/lgtm/grade/javascript/g/xofbd/unfair-coin-bayes.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/xofbd/unfair-coin-bayes/context:javascript)
 
 # Unfair Coin Bayesian Simulation
-This repository creates a web app that simulates the evolving probability distribution of an unfair coin to come up heads using Bayes's theorem. The prior distribution is a Beta distribution with both shape parameters set to one, resulting in a uniform distribution. This repository is ready to deploy a web application using [Flask](https://flask.palletsprojects.com) and [Bokeh](https://bokeh.org) to Heroku. An example of the app can be seen at https://unfair-coin-bayes.herokuapp.com.
+This repository creates a web app that simulates the evolving probability distribution of an unfair coin to come up heads using Bayes's theorem. The prior distribution is a Beta distribution with both shape parameters set to one, resulting in a uniform distribution. This repository is ready to deploy a web application using [Flask](https://flask.palletsprojects.com) and [Bokeh](https://bokeh.org) to services such as [Render](https://render.com/). An example of the app can be seen at [here](https://unfair-coin-bayes.onrender.com).
 
 ## Prerequisites
-You will need either Python 3.8 or 3.9. All required Python packages can be found in the `requirements.txt` file. You will also need a Heroku account and have installed the Heroku CLI. For more information on the Heroku CLI, go to https://devcenter.heroku.com/articles/heroku-cli#download-and-install.
+You will need either Python 3.8 or 3.9. All required Python packages can be found in the `requirements.txt` file.
 
-## Running the app locally using Flask
+## Running the app locally
 You may want to run the app using Flask locally before deploying it to Heroku, especially if you have made any changes to the code. To run locally:
 
 1. clone the repository.
@@ -23,14 +23,5 @@ Alternatively, you can deploy using [Docker](https://www.docker.com/). You can r
 1. `docker build -t unfair-coin-bayes .`
 1. `docker run --init --rm -d --publish 127.0.0.1:8000:8000 --env SECRET_KEY=$(bin/set-secret-key --) unfair-coin-bayes`
 
-## Deploying to Heroku
-Make sure your app is ready to be deployed to Heroku by running Flask locally. To deploy to Heroku:
-
-1. clone the repository (if you haven't yet).
-1. `heroku login` and enter your credentials.
-1. `heroku create` or `heroku create app-name` where app-name is a custom app name.
-1. `git push heroku master`.
-1. `heroku open` or open the app online through your Heroku profile.
-
 ## License
 This project is distributed under the MIT license. Please see `LICENSE` for more information.

bin/set-secret-key

@@ -1,12 +1,12 @@
 #!/bin/bash
 #
-# Set SECRET_KEY environmental variable for Heroku
+# Set SECRET_KEY environmental variable locally or to stdout
 # The key is a 32 random byte string in hexadecimal
 
 set -eu
 
 usage() {
-  echo "Usage: $0 {local|heroku|--}"
+  echo "Usage: $0 {local|--}"
 }
 
 [[ "$#" -ne 1 ]] && usage && exit 1
@@ -17,10 +17,7 @@ case "$1" in
   local)
     export SECRET_KEY="$key"
     ;;
-  heroku)
-    heroku config:set SECRET_KEY="$key"
-    ;;
-  --)
+   --)
     echo "$key"
     ;;
   *)