Update README.md (#490)

* Update README.md

Adding net-ldns to the list and a reference to the version list.

* Update README.md

Some edits.

* Update README.md

More fixes.

README.md

@@ -78,15 +78,26 @@ the source code.
 In order to install and run the different components, have a look at the
 installation documentation under each of the repositories below:
 
+ * [net-ldns](https://github.com/dotse/net-ldns) - which is a fork of
+   of [ldns](https://www.nlnetlabs.nl/projects/ldns/). with a Perl frontend
  * [zonemaster-engine](https://github.com/dotse/zonemaster-engine) - which
-   contains the test framework.
+   contains the libraries doing the actual tests.
  * [zonemaster-cli](https://github.com/dotse/zonemaster-cli) - a Command Line
    Interface for the engine.
  * [zonemaster-backend](https://github.com/dotse/zonemaster-backend) - which
    interfaces between the GUI and an API with the engine.
  * [zonemaster-gui](https://github.com/dotse/zonemaster-gui) - A graphical user
    interface for the engine.
 
+### Versions
+
+Go to the [release list](https://github.com/dotse/zonemaster/releases) 
+of this repository to find the 
+[latest version](https://github.com/dotse/zonemaster/releases/latest) of 
+Zonemaster and the versions of the specific components. Be
+sure to read the release note of each component before installing or
+upgrading.
+
 ### Participation
 
 The core development team are people from IIS and Afnic. However, you