Display ref{ra,le}ctive percentages
Calculate reflectance
Update ballsOnAPlane.scn to have refraction
First round of refraction

Totally doesn't work but it's a decent start to build off of.
Add refractiveIndex to Ray
Flip Sphere normal if inside of Sphere
Use castRay to do refractance rays

This meant including start and end materials in various places to
determine when to refract.
Update error text