Add supervisor installation instructions.

Closes #521

docs/installation/auth/index.md

@@ -8,5 +8,6 @@
     centos
     settings
     apache
+    supervisor
     quickstart
 ```

docs/installation/auth/supervisor.md

@@ -0,0 +1,63 @@
+# Supervisor
+
+>Supervisor is a client/server system that allows its users to control a number of processes on UNIX-like operating systems.
+
+What that means is supervisor will take care of ensuring the celery workers are running (and mumble authenticator) and start the automatically on reboot. Handy, eh?
+
+## Installation
+
+Most OSes have a supervisor package available in their distribution.
+
+Ubuntu:
+
+    sudo apt-get install supervisor
+
+CentOS:
+
+    sudo yum install supervisor
+    sudo systemctl enable supervisor.service
+    sudo systemctl start supervisor.service
+
+## Configuration
+
+Auth provides example config files for the celery workers (celeryd), the periodic task scheduler (celerybeat), and the mumble authenticator. All of these are available in `thirdparty/Supervisor`.
+
+For most users, all you have to do is copy the config files to `/etc/supervisor/conf.d` then restart the service. Copy `auth-celerybeat.conf` and `auth-celeryd.conf` for the celery workers, and `auth-mumble.conf` for the mumble authenticator. For all three just use a wildcard:
+
+    sudo cp thirdparty/Supervisor/* /etc/supervisor/conf.d
+
+Ubuntu:
+
+    sudo service supervisor restart
+
+CentOS:
+
+    sudo systemctl restart supervisor.service
+
+## Checking Status
+
+To ensure the processes are working, check their status:
+
+    sudo supervisorctl status
+
+Processes will be `STARTING`, `RUNNING`, or `ERROR`. If an error has occurred, check their log files:
+ - celeryd: `log/worker.log`
+ - celerybeat: `log/beat.log`
+ - authenticator: `log/authenticator.log`
+
+## Customizing Config Files
+
+The only real customization needed is if running in a virtual environment. The python path will have to be changed in order to start in the venv.
+
+Edit the config files and find the line saying `command`. Replace `python` with `/path/to/venv/python`. This can be relative to the `directory` specified in the config file.
+
+Note that for config changes to be loaded, the supervisor service must be restarted.
+
+## Troubleshooting
+
+### auth-celerybeat fails to start
+Most often this is caused by a permissions issue on the allianceauth directory (the error will talk about `celerybeat.pid`). The easiest fix is to edit its config file and change the `user` from `allianceserver` to `root`.
+
+### Workers are using old settings
+
+Every time the codebase is updated or settings file changed, workers will have to be restarted. Easiest way is to restart the supervisor service (see configuration above for commands)