Include Uploads example notebook

[jisantuc]

Overview

This PR adds a notebook showing how to work with uploads and an aws module that currently only includes functions for authorizing and unauthorizing Raster Foundry to read from buckets.

Testing

• try to authorize a bucket that you have credentials for using aws.s3.authorize_bucket
• verify that the policy gets attached appropriately in the aws console
• try to unauthorize that bucket
• verify that the policy gets removed in the aws console
• run through the uploads notebook and make sure it makes sense and works

Starts on #16