Added example reward functions.

reward-example-self-motivation.py

@@ -0,0 +1,8 @@
+def reward_function(params):
+
+    if params["all_wheels_on_track"] and params["steps"] > 0:
+        reward = ((params["progress"] / params["steps"]) * 100) + (params["speed"]**2)
+    else:
+        reward = 0.01
+
+    return float(reward)