Use ES6 build for the main library entry point (#34)

Author: bnjm

package.json

@@ -2,7 +2,7 @@
   "name": "ray-tracing-renderer",
   "version": "0.2.0",
   "description": "A [Three.js](https://github.com/mrdoob/three.js/) renderer which utilizes path tracing to render a scene with true photorealism. The renderer supports global illumination, reflections, soft shadows, and realistic environment lighting.",
-  "main": "src/main.js",
+  "main": "build/RayTracingRenderer.js",
   "scripts": {
     "build": "./node_modules/.bin/rollup -c",
     "dev": "./node_modules/.bin/rollup -cw --environment DEV & ./node_modules/.bin/http-server",