Remove Heroku deploy button

Procfile

@@ -1 +0,0 @@
-web: bundle exec unicorn -p $PORT -c ./config/unicorn.rb

README.md

@@ -4,35 +4,33 @@
 
 [Frankfurter](https://www.frankfurter.app) is a free and open-source currency data API that tracks reference exchange rates published by the European Central Bank.
 
-I host a public instance of the API at `api.frankfurter.app`.
+`api.frankfurter.app` hosts a public instance of the API.
 
 ## Getting Started
 
 Get the latest exchange rates.
 
-```http
-GET /latest HTTP/1.1
+```
+https://api.frankfurter.app/latest
 ```
 
 Get rates for a past date.
 
-```http
-GET /2000-01-03 HTTP/1.1
+```
+https://api.frankfurter.app/2000-01-03
 ```
 
 Get rates for a period.
 
 ```http
-GET /2010-01-01..2010-01-31 HTTP/1.1
+https://api.frankfurter.app/2010-01-01..2010-01-31
 ```
 
 For more examples, read the [docs](https://www.frankfurter.app/docs).
 
 ## Deployment
 
-[![Deploy](https://www.herokucdn.com/deploy/button.svg)](https://heroku.com/deploy?template=https://github.com/hakanensari/frankfurter)
-
-You can self-host Frankfurter with Heroku or Docker.
+You can self-host Frankfurter with Docker.
 
 ```bash
 docker run -d -p 8080:8080 \
@@ -40,8 +38,6 @@ docker run -d -p 8080:8080 \
   --name frankfurter hakanensari/frankfurter
 ```
 
-Check out the [website](https://www.frankfurter.app/docs#deployment) for a more detailed walkthrough.
-
 ## Miscellaneous
 
 Frankfurter was known as Fixer between 2012 and 2018. After selling the original domain, I relaunched under this name.

app.json

@@ -1,16 +0,0 @@
-
-{
-  "name": "Frankfurter",
-  "description": "Foreign exchange rates and currency conversion API",
-  "website": "https://frankfurter.app",
-  "repository": "https://github.com/hakanensari/frankfurter",
-  "logo": "https://frankfurter.app/images/frankfurter.png",
-  "keywords": [
-    "exchange rate",
-    "currency",
-    "conversion"
-  ],
-  "addons": [
-    "heroku-postgresql"
-  ]
-}