add thoughts on DIP

[klaeufer]

https://en.wikipedia.org/wiki/Dependency_inversion_principle <- good reference
The key points of the principle are

• High-level modules should not import anything from low-level modules. Both should depend on abstractions (e.g., interfaces).
• Abstractions should not depend on details. Details (concrete implementations) should depend on abstractions.

Let's try to map these points to an example, such as LineCountImperativeModular together with the common traits. Which of those traits and objects are

• high-level modules
• low-level modules
• abstractions
• details

?

Or perhaps we could arrange the traits along a high-level vs. low-level continuum.
It would be great if some of you followed up here so we can have a discussion!