clarify tool name and supported boards/OSes

Signed-off-by: Eystein Måløy Stenberg <eystein.maloy.stenberg@northern.tech>

README.md

@@ -1,11 +1,13 @@
-Mender Conversion Tool
-======================
+mender-convert
+==============
 
 Mender is an open source over-the-air (OTA) software updater for embedded Linux devices. Mender comprises a client running at the embedded device, as well as a server that manages deployments across many devices.
 
-This repository contains the Mender Conversion Tool, which is used to convert pre-built disk images (Debian, Ubuntu, Raspbian, etc) to a Mender compatible
+This repository contains mender-convert, which is used to convert pre-built disk images (Debian, Ubuntu, Raspbian, etc) to a Mender compatible
 image by restructuring partition table and injecting the necessary files.
 
+Currently official Raspberry Pi 3 and BeagleBone Black images are supported and this will be extended.
+
 ![Mender logo](https://mender.io/user/pages/resources/06.digital-assets/mender.io.png)
 
 ## Getting started