Add hint how to use this stuff

I guess some guys are trying to execute EV3 Manager on their computers .... ;-)

Author: cyborg-x1

README.md

@@ -1,5 +1,9 @@
 # h4r_ev3_ctrl
 
+:warning: **ATTENTION! THE EV3_MANAGER NODE IS SUPPOSED TO RUN ON THE EV3 BRICK DIRECTLY!** :warning:
+
+Use the image in the instructions - it gives you all except for the launchfiles you should launch on your Linux PC to make the Brick load the controller!
+
 Instructions to get a working image for your SD Card can be found here:
 
 http://hacks4ros.github.io/h4r_ev3_ctrl/