Refactor LoadsAndAuthorizesResource

[jagthedrummer]

Picking up #263 to get it over the finish line.

This PR does the following:

1. Namespaces LoadsAndAuthorizesResource to BulletTrain::LoadsAndAuthorizesResource. This will allow client apps to reference the module still if their app also defines LoadsAndAuthorizesResource.
2. Maintains backward compatibility by still defining LoadsAndAuthorizesResource and having it include BulletTrain::LoadsAndAuthorizesResource.
3. Gets rid of the included block, as it was unnecessary.
4. Wraps class methods in a class_methods block and removes self.

Thanks to @aaricpittman for doing all the heavy lifting on this one. I just had to make a few tiny changes to make the linter happy.