make PsychoPy minimum working examples

[drbenvincent]

Make a simple minus working example. This will be much like the current demo experiment, but without the chooser.py which might confuse things for people.

This will also act as a good skeleton experiment to copy and paste to start off new experiments with.

• [x] delayed choice minimum working example
• [x] risky choice minimum working example
• [ ] example for a blocked design
• [ ] example for multiple model fitting