update README re. how to locally run s2i

now that we don't have a Dockerfile here anymore, "docker build" was
wrong of course; we now need to "s2i build" - incl. parent images.

README.md

@@ -69,9 +69,17 @@ You can obviously mix the order and repeat titles, comments, chats, narrations,
 
     ./gradlew build
 
-In Docker:
+With S2I, and with git reset and clean due to #28 and #71:
 
-    docker build -t minecraft-storeys-maker .
+    cd ../s2i/java/images/jboss
+    docker build . -t fabric8/s2i-java
+
+    cd ../s2i-minecraft-server
+    s2i build --copy . fabric8/s2i-java s2i-minecraft-server
+
+    cd ../minecraft-storeys-maker
+    git reset --hard; git clean -d -f -x
+    s2i build --copy . s2i-minecraft-server minecraft-storeys-maker
 
     docker run --rm -p 25565:25565 -p 8080:8080 -p 7070:7070 minecraft-storeys-maker