Revise process for getting new devs access to data

[xmedr]

The current documented process for onboarding folks onto this project doesn't work for a couple reasons:

1. the mentioned repo where the dev data is supposed to live does not exist
2. the makefile is currently erroring out if you do try to use it on the dev data

Let's go ahead and revise it a bit. Here's some things we can try to make this process a bit easier going forward:

• Create an s3 bucket to house a fixture created with the dumpdata management command.
• Update the readme to instead instruct people to go and download that file, and load it in using loaddata.
• See if we can create a fixture from the data in either the production or staging instance.
• If we can, then upload that to the bucket and update the readme with instructions for updating the fixture. If not, then the fixture that we already have also works.