Fix README

See heroku/heroku-buildpack-apt#23

README.md

@@ -7,11 +7,13 @@ This buildpack depends on [heroku-buildpack-apt](https://github.com/heroku/herok
 You must configure the buildpacks in the following order:
 
 ```bash
-heroku buildpacks:add https://github.com/heroku/heroku-buildpack-apt --index 1
+heroku buildpacks:add https://github.com/sobrinho/heroku-buildpack-apt --index 1
 heroku buildpacks:add https://github.com/sobrinho/heroku-buildpack-pgpool --index 2
 heroku buildpacks:add https://github.com/heroku/heroku-buildpack-ruby --index 3
 ```
 
+**Important:** You have to use [my fork](https://github.com/sobrinho/heroku-buildpack-apt) of [heroku-buildpack-apt](https://github.com/heroku/heroku-buildpack-apt) until https://github.com/heroku/heroku-buildpack-apt/pull/23 get merged.
+
 _heroku-buildpack-ruby is not a dependency, it's an example of an application buildpack which must be the latest, you may use whatever you want._
 
 Remember that if your application is already deployed, you may not need the 3rd command as your application buildpack will be already set.