Update INSTALL-ubuntu.md

This uses the new environment variables; by duplicating the sample config and suggesting similar changes. It's not exactly perfect as it still has the sample config problem, just to a much lesser extent. It may help to ship a "most commonly changed" configuration [db name + user/pass, hostname, smtp] that can be duplicated from and easily edited.

Follows up:
http://meta.discourse.org/t/environment-variables/11494/5

docs/INSTALL-ubuntu.md

@@ -168,28 +168,18 @@ Configure Discourse:
 
     # Run these commands as the discourse user
     cd /var/www/discourse/config
-    cp database.yml.production-sample database.yml
-    cp redis.yml.sample redis.yml
-    cp discourse.pill.sample discourse.pill
-    cp environments/production.rb.sample environments/production.rb
+    cp discourse_defaults.conf discourse.conf
 
-Edit /var/www/discourse/config/database.yml
+Editing /var/www/discourse/config/discourse.conf:
 
-- change production database name if appropriate
+Database/Hostname:
 - change database username/password if appropriate
-- if you are hosting multiple Discourse forums on the same server (multisite), set `db_id`
-- change `host_names` to the name you'll use to access the discourse site, e.g. "forum.example.com"
-
-Edit /var/www/discourse/config/redis.yml
+- change `hostname` to the name you'll use to access the discourse site, e.g. "forum.example.com"
 
+Redis:
 - no changes if this is the only application using redis, but have a look
 
-Edit /var/www/discourse/config/discourse.pill
-
-- change application name from 'discourse' if necessary
-- Ensure appropriate Bluepill.application line is uncommented
-
-Edit /var/www/discourse/config/environments/production.rb
+E-mail:
 - browse througn all the settings
 - be sure to add your mail server SMTP settings so outgoing mail can be sent (we recommend [Mandrill](https://mandrillapp.com))
 - If your users will come from "internal" [private unroutable IPs](https://en.wikipedia.org/wiki/Private_network) like 10.x.x.x or 192.168.x.x please [see this topic](http://meta.discourse.org/t/all-of-my-internal-users-show-as-coming-from-127-0-0-1/6607).