Add entry to readme about use without PuppetDB

Author: zipkid

README.md

@@ -16,22 +16,30 @@
 
 #### Table of Contents
 
-1. [Overview](#overview)
-1. [Module Description](#module-description)
-1. [Setup](#setup)
-    1. [Set up node discovery](#set-up-node-discovery)
-    1. [Set up auth.conf](#set-up-auth-conf)
-1. [Usage](#usage)
-    1. [Multi threaded compile requests](#multi-threaded-compile-requests)
-    1. [Fact search](#fact-search)
-    1. [Changed depth](#changed-depth)
-    1. [Output report](#output-report)
-1. [Limitations](#limitations)
-1. [Previous Authors](#previous-authors)
-1. [Contributors](#contributors)
-1. [See Also](#see-also)
-    1. [Upload facts to PuppetDB](#upload-facts-to-puppetdb)
-    1. [Modern fact submission](#modern-fact-submission)
+- [Puppet Catalog Diff](#puppet-catalog-diff)
+      - [Table of Contents](#table-of-contents)
+  - [Overview](#overview)
+  - [Module Description](#module-description)
+  - [Setup](#setup)
+    - [Set up node discovery](#set-up-node-discovery)
+    - [Set up auth.conf](#set-up-authconf)
+  - [Usage](#usage)
+    - [Multi threaded compile requests](#multi-threaded-compile-requests)
+    - [Fact search](#fact-search)
+    - [Node list](#node-list)
+    - [Changed depth](#changed-depth)
+    - [Output Report](#output-report)
+    - [Non-default PuppetDB/Configuring PuppetDB](#non-default-puppetdbconfiguring-puppetdb)
+      - [Use without PuppetDB](#use-without-puppetdb)
+    - [Non-default Puppetserver](#non-default-puppetserver)
+  - [Limitations](#limitations)
+  - [Previous Authors](#previous-authors)
+  - [Contributors](#contributors)
+  - [See also](#see-also)
+    - [Upload facts to PuppetDB](#upload-facts-to-puppetdb)
+    - [Modern fact submission](#modern-fact-submission)
+    - [complex fact submission](#complex-fact-submission)
+    - [Further documentation](#further-documentation)
 
 
 ## Overview
@@ -293,6 +301,12 @@ via CLI options Those are:
 * `--old_puppetdb_tls_key=`
 * `--old_puppetdb_tls_ca=`
 
+#### Use without PuppetDB
+
+It is possible to use this module without PuppetDB.
+If the libraries for PuppetDB are not installed, the module will set the
+puppet_url parameter to `https://puppetdb:8081` and will not use PuppetDB.
+
 ### Non-default Puppetserver
 
 `puppet catalog diff` can request an old catalog from a Puppetserver. The