Update `command` description

The docs were a little bit out of date with what commands are available to be run. They also didn't explain that you could pass custom commands - I almost went down the path of trying to run our custom management commands with the generic Ansible `command` module.

library/web_infrastructure/django_manage

@@ -28,9 +28,9 @@ description:
 version_added: "1.1"
 options:
   command:
-    choices: [ 'cleanup', 'flush', 'loaddata', 'runfcgi', 'syncdb', 'test', 'validate', 'migrate', 'collectstatic' ]
+    choices: [ 'cleanup', 'collectstatic', 'flush', 'loaddata', 'migrate', 'runfcgi', 'syncdb', 'test', 'validate', ]
     description:
-      - The name of the Django management command to run. Allowed commands are cleanup, createcachetable, flush, loaddata, syncdb, test, validate.
+      - The name of the Django management command to run. Built in commands are cleanup, collectstatic, flush, loaddata, migrate, runfcgi, syncdb, test, and validate. Other commands can be entered, but will fail if they're unknown to Django.
     required: true
   app_path:
     description: