add os dependencie

README.md

 
 Tested only under linux, debian/Ubuntu. Before install project, install OS packages:
 
-    build-essential libsdl1.2debian libsdl-image1.2 libsdl-image1.2-dev libsdl-ttf2.0-0 libsdl-ttf2.0-dev libsdl-mixer1.2 libsdl-mixer1.2-dev redis-server
+    build-essential python3-tk libsdl1.2debian libsdl-image1.2 libsdl-image1.2-dev libsdl-ttf2.0-0 libsdl-ttf2.0-dev libsdl-mixer1.2 libsdl-mixer1.2-dev redis-server
 
 Python version: 3.5+