Update README.md

README.md

 
 * python3.4+
 * pygame (see [here](http://www.pygame.org/wiki/CompileUbuntu#Python%203.x) for pygame python3 installation)
-* requirements.txt dependencies
+* requirements.txt dependencies (install them with pip install -r requirements.txt)
 
 Then run ``run.py exploration`` or ``run.py all``. Keep in mind it's in developpment mode !