[ci skip] Consolidate advanced-installation instructions and simplify the install guide

Also move vagrant instructions into their own file

docs/getting-started/install/vagrant.md

@@ -0,0 +1,39 @@
+# Install Dokku using Vagrant
+
+- Download and install [VirtualBox](https://www.virtualbox.org/wiki/Downloads)
+- Download and install [Vagrant](http://www.vagrantup.com/downloads.html)
+- Clone Dokku
+
+    ```
+    git clone https://github.com/progrium/dokku.git
+    ```
+
+- Setup SSH hosts in your `/etc/hosts`
+
+    ```
+    10.0.0.2 dokku.me
+    ```
+
+- Create VM
+    ```
+    # Optional ENV arguments:
+    # - `BOX_NAME`
+    # - `BOX_URI`
+    # - `BOX_MEMORY`
+    # - `DOKKU_DOMAIN`
+    # - `DOKKU_IP`.
+    cd path/to/dokku
+    vagrant up
+    ```
+- Setup SSH Config in `~/.ssh/config`. The port listed here is usually correct, though you may want to verify that it is the same as the one listed in the output of `vagrant ssh-config dokku`
+
+    ```
+    Host dokku.me
+        Port 2222
+    ```
+
+- Copy your SSH key via `cat ~/.ssh/id_rsa.pub | pbcopy` and paste it into the dokku-installer at http://dokku.me . Change the `Hostname` field on the Dokku Setup screen to your domain and then check the box that says `Use virtualhost naming`. Then click *Finish Setup* to install your key. You'll be directed to application deployment instructions from here.
+
+You are now ready to deploy an app or install plugins.
+
+For a different, complete, example see https://github.com/RyanBalfanz/dokku-vagrant-example.