More Shapes/Primitives!

[cqann]

I suggest that more shapes should be added to PyPen!
More specifically these primitives should be added:

• Triangle
• Line
• Custom Shape (with begin_shape and end_shape)
• potentially square, equilateral_triangle, point (just a pixel) and curve

[EriKWDev]

N-gon, centered_rectangle and centered_square :3 (if we don't implement them in a different way)

[cqann]

I agree that shapes such as rectangles should be able to be centered, but I don't believe that they should have their own primitives. Instead I'm suggesting that we maybe implement a rectangle_mode, either a function or variable. This would contain info which would be checked in the rectangle primitive, and translation would then be carried out there.

[EriKWDev]

Different modes seems like a good idea :) settings.rectangle_mode = "normal" | "center"/"middle" could do that.
We should probably, speaking of modes, also have settings.angle_mode = "degrees" | "radians"

[EriKWDev]

Instead I'm suggesting that we maybe implement a rectangle_mode, either a function or variable

see #17