change datatype of timestep from int to float

app/src/main/java/de/hems/trafficsim/VehicleTimeRecord.java

@@ -16,9 +16,9 @@ public class VehicleTimeRecord {
     protected int id;
     protected float position;
     protected float velocity;
-    protected int timestep;
+    protected float timestep;
 
-    public VehicleTimeRecord(int id, float position, float velocity, int timestep) {
+    public VehicleTimeRecord(int id, float position, float velocity, float timestep) {
         this.id = id;
         this.position = position;   //needed???
         this.velocity = velocity;