Add app.json manifest, update documentation

Author: fionn

README.md

@@ -1,16 +1,19 @@
 # Automatically Managed DNS
 
-A system to automate the management of DNS A records for a large number of servers.
+A system to automate the management of DNS A records for an arbitrary number of servers.
 
 ## Run
 
 ### Locally
 
 Clone, set up a virtual environment with `make venv` and enter it with `source venv/bin/activate`.
 
-The application expects AWS API secrets as the environment variables `AWS_ACCESS_ID`, `AWS_ACCESS_SECRET`.
+The application expects AWS API secrets as the environment variables `AWS_ACCESS_ID`, `AWS_ACCESS_SECRET` and a pseudo-random `SECRET_KEY`.
 
-Then run with `./run.py` to serve the web interface on `localhost:5000`. In `dns.create_instances()` some toy data is created.
+Run with `./run.py` or `flask run` to serve the web interface in development mode on `localhost:5000` with Flask. To serve with `gunicorn` on `localhost:8000`, run the command in `Procfile`. Simulate a deployment with `heroku local`.
 
-Currently deployed to [lit-tundra-97584.herokuapp.com](https://lit-tundra-97584.herokuapp.com/).
+Some toy data is created in `dns.create_instances`.
 
+### Deploy
+
+[![Deploy](https://www.herokucdn.com/deploy/button.svg)](https://heroku.com/deploy?template=https://github.com/fionn/dns-automator)

app.json

@@ -0,0 +1,19 @@
+{
+    "name": "DNS Automator",
+    "description": "Stub DNS management for Server Admin",
+    "keywords": ["DNS", "route53", "AWS", "Flask"],
+    "repository": "https://github.com/fionn/dns-automator",
+    "success_url": "/",
+    "env": {
+        "SECRET_KEY": {
+            "description": "Secret key for signing cookies",
+            "generator": "secret"
+        },
+        "AWS_ACCESS_ID": {
+            "description": "AWS key ID"
+        },
+        "AWS_ACCESS_SECRET": {
+            "description": "AWS secret token"
+        }
+    }
+}