Write unit tests for spatial_transformations.py

[Chad-Peterson]

Right now spatial_transformations.py contains two functions: translate and rotate_about_point. These calculations need unit tests.

Reminder: Please include an illustration of each test case in the associated test folder. This could be a hand-drawn picture or a screenshot of a PowerPoint slide. I'll figure out a standard format later.

[Chad-Peterson]

Clarification: For now, please attach any work you do by hand as a PNG/JPG/PDF/PPT when you respond to this issue. In the future, when we create actual visualization, we will refer back to this chat.

[Chad-Peterson]

TODO: Confirm if finite differencing the rotation angles returns the object to its original position or if I need to invert the rotation matrix somehow (inverting is easy, but knowing when to invert requires logic).

Currently, to avoid components drifting from FD, we avoid this problem by only calculating the FD positions and not actually setting the component position with each step.