Add real traffic light detection sample code

[yaboo-oyabu]

Add real traffic light detection sample code, and update the default TensorFlow version to 1.15.

[jotredi]

I have tried your code with images from the simulator as well. I think we could use it for detect traffic lights from both the simulator and real images.

The model detects near traffic lights pretty well with a confidence cutoff of 0.4

However, is not able to detect traffic lights that are far away from the vehicle (around 300 waypoints) even if I take down the confidence cutoff

but as soon as it approaches the traffic light it starts detecting some of them:

Even though it doesn't detect traffic lights that are far away, it detects them soon enough for the car to brake smoothly. For me, we can use this detector :)

[yaboo-oyabu]

@jotredi Thanks for the check. Could you kindly approve my pull request? I need someone's approval before the merge.