Start on the rasteriser implementation

run

@@ -3,8 +3,8 @@
 USAGE="Usage: run (raytracer | rasteriser)"
 
 if [[ $# == 0 ]]; then
-	echo $USAGE
-	exit 1
+  echo $USAGE
+  exit 1
 fi
 
 while [[ $# -gt 0 ]]; do
@@ -13,8 +13,12 @@ while [[ $# -gt 0 ]]; do
       RENDERER="raytracer"
       shift # past argument
       ;;
+    rasteriser)
+      RENDERER="rasteriser"
+      shift # past argument
+      ;;
     -*|--*|*)
-			echo $USAGE
+      echo $USAGE
       exit 1
       ;;
   esac