Remove reference to pm2

Remove the instructions for installing and using pm2 with clusterio, as
I don't know how to use this tool properly and can't keep the README up
to date on it.

README.md

@@ -116,10 +116,6 @@ Master and all slaves:
 
 downloads and installs nodejs, git and clusterio. To specify a version, change "latest" in the link to a version number like 0.14.21.
 
-Optional step (if you want to use pm2):
-
-    sudo npm install pm2 -g
-
 **Ubuntu with Docker**
 
 The Docker support for Clusterio is curently broken.  If you need it
@@ -200,10 +196,6 @@ up:
 
     node master run
 
-Or with pm2 (it's recommened to run it without pm2 first):
-
-    pm2 start master --name master
-
 
 ### Slaves