itertools readme update for traffic lights instruction set

Author: hobojoe1848

days/19-21-itertools/README.md

@@ -16,6 +16,10 @@ After watching the first 4 videos pop into your Python shell and start playing a
 
 Yep that's right! For your second day, use itertools to create a script that simulates traffic lights!
 
+The idea is to perhaps... *cycle* (hint hint!) through the different colours of a set of traffic lights - red, amber and green - printing the name of the colour every time the cycle occurs. 
+
+For bonus points: traffic lights normally cycle between green and red based on traffic levels so you never know exactly when the change will happen. This is a great chance to throw some randomness into your script.
+
 If you get absolutely stuck, watch the *Traffic Lights* video to see how we did it.
 
 
@@ -40,4 +44,4 @@ Be sure to share your last couple of days work on Twitter or Facebook. Use the h
 
 Here are [some examples](https://twitter.com/search?q=%23100DaysOfCode) to inspire you. Consider including [@talkpython](https://twitter.com/talkpython) and [@pybites](https://twitter.com/pybites) in your tweets.
 
-*See a mistake in these instructions? Please [submit a new issue](https://github.com/talkpython/100daysofcode-with-python-course/issues) or fix it and [submit a PR](https://github.com/talkpython/100daysofcode-with-python-course/pulls).*
+*See a mistake in these instructions? Please [submit a new issue](https://github.com/talkpython/100daysofcode-with-python-course/issues) or fix it and [submit a PR](https://github.com/talkpython/100daysofcode-with-python-course/pulls).*