Update worker document for setproctitle feature (#1109)

* Replace procname with setproctitle

* Document process title feature

* Fix typo

docs/docs/workers.md

@@ -95,7 +95,7 @@ The life-cycle of a worker consists of a few phases:
 8. _Loop_.  Repeat from step 3.
 
 
-## Performance Notes
+### Performance Notes
 
 Basically the `rq worker` shell script is a simple fetch-fork-execute loop.
 When a lot of your jobs do lengthy setups, or they all depend on the same set
@@ -219,6 +219,12 @@ worker.failed_job_count # Number of failed jobs processed by this worker
 worker.total_working_time  # Amount of time spent executing jobs (in seconds)
 ```
 
+## Better worker process title
+Worker process will have a better title (as displayed by system tools such as ps and top) 
+after you installed a third-party package `setproctitle`:
+```sh
+pip install setproctitle
+```
 
 ## Taking Down Workers