Add doc

README.md

@@ -121,6 +121,8 @@ Docker is great for quickly trying out software, but it has its drawbacks too. I
 
 [![Deploy on Scalingo](https://cdn.scalingo.com/deploy/button.svg)](https://my.scalingo.com/deploy?source=https://github.com/tootsuite/mastodon#master)
 
+[You can view a guide for deployment on Scalingo here.](docs/Running-Mastodon/Scalingo-guide.md)
+
 ## Deployment on Heroku (experimental)
 
 [![Deploy](https://www.herokucdn.com/deploy/button.svg)](https://heroku.com/deploy)

docs/Running-Mastodon/Scalingo-guide.md

+Scalingo guide
+==============
+
+[![Deploy on Scalingo](https://cdn.scalingo.com/deploy/button.svg)](https://my.scalingo.com/deploy?source=https://github.com/tootsuite/mastodon#master)
+
+1. Click the above button.
+2. Fill in the options requested.
+  * You can use a .scalingo.io domain, which will be simple to set up, or you can use a custom domain.
+  * You will want Amazon S3 for file storage. The only exception is for development purposes, where you may not care if files are not saved. Follow a guide online for creating a free Amazon S3 bucket and Access Key, then enter the details.
+  * If you want your Mastodon to be able to send emails, configure SMTP settings here (or later). Consider using [Mailgun](https://mailgun.com) or similar, who offer free plans that should suit your interests.
+3. Deploy! The app should be set up, with a working web interface and database. You can change settings and manage versions from the Heroku dashboard.
+
+You may need to use the `scalingo` CLI application to run `USERNAME=yourUsername rails mastodon:make_admin` to make yourself an admin.