Revert "Remove node pm2 global install; install pm2 locally from now on"

This reverts commit 1e314da.

nodejs/pm2.sls

@@ -0,0 +1,22 @@
+include:
+  - jcu.nodejs
+
+pm2:
+  npm.installed:
+    - require:
+      - pkg: nodejs
+
+# Command should be re-run if nodejs or pm2 are modified
+pm2 startup:
+  cmd.run:
+    - prepend_path: /usr/local/bin
+    - onchanges:
+      - npm: pm2
+      - pkg: nodejs
+
+# Use onchanges_in in remote states to have pm2 save after their introduction
+pm2 save:
+  cmd.run:
+    - prepend_path: /usr/local/bin
+    - require:
+      - npm: pm2