Some json files are incorrect or not properly defined

[Dxyk]

Hi, I was testing on the given JSON data files and realized that some files are incorrectly defined.

• triangle.json currently outputs a square instead of a triangle because of line 18. [0,8660254038,0] should be [0,0.8660254038,0]. The second element is missing a 0.
• inside-a-sphere.json and two-spheres-and-plane.json give segmentation faults because they're missing the materials attribute.

[abhimadan]

Thanks for pointing this out. The scene files have been updated to include lights and materials; pull to get the changes.

[abhimadan]

There were some questions about this during today's tutorial, so I'm reopening this issue for visibility.