[WIP] Refactor colors

[adamaaronson]

🚨 This is a breaking change, affecting the parameters when defining shapes and setting a scene's background color. 🚨

Addresses issue #449.

Done:

• Created colors module to represent RGB colors
• Refactored Shape colors, Scene background color, and Text color to use the new Color class
• Fixed example code and test code to use the new Color class
• Write tests for colors

Next steps:

• Add more ways to define colors (by hex? by name?)

[AstraLuma]

Do we want to call this RGB instead?

[AstraLuma]

I would rather have HSV().to_rgb()?

@pathunstrom your thoughts?

[adamaaronson]

Concerned about that approach - I think there should only be one class for color so that it is intuitive to users that that’s the class they should plug in whenever they need to use a color. Don’t want people to accidentally use an HSV color when the class is expecting an RGB color, for example.

[adamaaronson]

I decided to refactor it into an abstract base class Color, with RGBColor and HSVColor subclasses that all have a to_rgb() method that should generally be abstracted away from the user. Let me know what you think!