docs: Clarify prerequisites to deploying on Dokku

Author: sman591

docs/deployment-dokku.md

@@ -3,16 +3,20 @@ id: deployment-dokku
 title: Dokku Deployment
 ---
 
-Below are steps & notes to deploy HackathonManager on Dokku. This assumes you already have [Dokku](http://dokku.viewdocs.io/dokku/) running on a machine and can SSH into the box. DNS should likely be set up as well, but isn't required for bare minimum functionality.
+Below are steps & notes to deploy HackathonManager on Dokku.
+
+>This assumes you already have a virtual machine with [Dokku](http://dokku.viewdocs.io/dokku/) running on it, and can SSH into the VM. DNS should be set up as well, but isn't required for bare minimum functionality.
+>
+>If you need a VM, check out [DigitalOean](https://m.do.co/c/b5ee103e23c3) or [Linode](https://www.linode.com/?r=e90a6fb2a6999fb4ec7b60b1add3e288f97954bf) and the [Dokku docs](http://dokku.viewdocs.io/dokku/) to get started.
 
 If you have any questions at all, please don't hesitate to reach out to [Stuart](https://github.com/sman591)! This doc is very much a work in progress but we want to keep it as up to date as possible.
 
 ## Dokku plugins
 
 Currently used and required Dokku plugins (other than the defaults):
 
-- [MySQL](https://github.com/dokku/dokku-mysql)
-- [Redis](https://github.com/dokku/dokku-redis) (required by Sidekiq)
+- [MySQL](https://github.com/dokku/dokku-mysql) (data storage)
+- [Redis](https://github.com/dokku/dokku-redis) (background jobs + caching)
 - [dokku-letsencrypt](https://github.com/dokku/dokku-letsencrypt) (Optional: free, automated SSL certificates)
 
 ### Dokku Setup Steps