Add docs for customizing Redis, add example file

config/resque.yml.example

@@ -0,0 +1,3 @@
+development: localhost:6379
+test: localhost:6379
+production: redis.example.com:6379

doc/installation.md

@@ -251,6 +251,14 @@ You can login via web using admin generated with setup:
     # if you run this as root /home/gitlab/gitlab/tmp/pids/resque_worker.pid will be owned by root
     # causing the resque worker not to start via init script on next boot/service restart
 
+## Customizing Resque's Redis connection
+
+If you'd like Resque to connect to a Redis server on a non-standard port or on
+a different host, you can configure its connection string in the
+**config/resque.yml** file:
+
+    production: redis.example.com:6379
+
 **Ok - we have a working application now. **
 **But keep going - there are some things that should be done **
 
@@ -276,7 +284,6 @@ You can login via web using admin generated with setup:
     # of the host serving GitLab.
     sudo vim /etc/nginx/sites-enabled/gitlab
 
-
     # Restart nginx:
     /etc/init.d/nginx restart