Added custom functions to loop

examples/particles/src/main.rs

@@ -1,9 +1,16 @@
 use hypoloop::Simulation;
 
+// look into using closures for this
 fn main() {
-    // create sim
+    // create sim and configure it
     let mut sim = Simulation::new();
+    sim.set_update_function(test);
+    //sim.set_realtime(false);
 
     // run sim
     sim.run();
 }
+
+fn test() {
+    println!("Test");
+}