Added ray module

src/ray.rs

@@ -0,0 +1,15 @@
+use nalgebra::Vector4;
+
+pub struct Ray {
+    a: Vector4<f32>,
+    b: Vector4<f32>,
+}
+
+impl Ray {
+    fn new(_a: Vector4<f32>, _b: Vector4<f32>) -> Ray {
+        Ray { a: _a, b: _b }
+    }
+    fn at_t(self, t: f32) -> Vector4<f32> {
+        self.a + self.b * t
+    }
+}