Adds *nix machine requirement to README.md

Change-Id: I084fd446b6727857b6cfe67ae7ae524fa21c5896
diff --git a/README.md b/README.md
index c66b728..b5e9a6a 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@
 **DISCLAIMER**: The data shown in the website might be wrong due to a wrong implementation.
 
 ## Requirements
-These programs should be installed in order to generate the graphs:
+Only \*NIX machines (essentially a PC with a Linux distro or a Mac) are supported. These programs should be installed in order to be able to generate the graphs:
 
 * PHP (at least version 7)
 * gnuplot (at least version 5.2)