updated readme

README.md

@@ -13,16 +13,10 @@ cabinets, or for interaction, e.g. controlling sound with 3D widgets.
 For video examples of what Rivill can do, watch https://vimeo.com/album/4703717
 
 Rivill has been used in the following projects:
-* http://ixmi.hitmuri.net
 * https://www.cristal.univ-lille.fr/mint/revealable-volume-displays.html
 * https://www.cristal.univ-lille.fr/mint/revealed-interfaces.html
 * https://terrev.univ-lille.fr/
 
-## Help 
-A tutorial describing the main components of Rivill is available 
-in [the doc folder](doc/tutorial.md).
-Several examples are also provided.
-
 ## Software requirements:
 * OpenGL >= 4.3 (or >=3 but there will be no revealing output)