Implement AWS connection

- Add aws-sdk gem to connect with Amazon S3 Bucket
- Add index method for SongController
- Add layout for songs#index to list all songs in Bucket
- Add upload and delete, but they still need work.
- Add sanitize name method to uploaded files.
- Add resources routes for songs. Unused routes will be deleted later.
- Working! songs#index page is displaying all songs in my AWS bucket.