Very nice! Just for the sake of completeness, here are a few other resources related to the double pendulum.

1. Wolfram Language knows this system and its properties, for example:

   

2. You can ask Wolfram|Alpha and get complete equations of motion, plots, and even interactive interfaces!

3. There is a complete example in docs.

   

4. There is an article in ScienceWorld. In contrast with Wikipedia, that considers joined rods system with distributed mass, the ScienceWorld shows equations for exactly your system of coupled masses:

   

5. There is a demonstration by Rob Morris: Double Pendulum