Removed Devise, added basic authentication

Here is what I did:

I created a migration to get rid of the fields that Devise left behind. I also got rid of the Devise files.
The basic authentication is there. Data sets, sources, and tags can not be modified or destroyed by non-users. It will just redirect you to the login page.

One caveat: If you login with the wrong password, it will give you a 'template missing' error instead of returning you to the login page. I cannot figure out how to display the error in the view using form_tag .

I know we talked about users only being able to delete their data sets, sources, and tags and not others', but I would rather set up Rspec and get some tests up before I tackle those issues.
Aahhh, Rails generators. They're great because they give you a bunch of quick files to start working with. They're sloppy because they give you a bunch of quick files that you may not want!

If we want to add styles or javascripts that are only relevant to sessions or users later on, we can do that then. For now, since these files are empty, let's get rid of them. :joy_cat: