Create tests and automate for new PRs

[lsterzinger]

As @martindurant mentioned in #58 we should probably get some tests created with the example_* functions and run them automatically with new PRs. I think this can be relatively easy to do with GitHub actions.

[lsterzinger]

Thinking about the best way to create tests. I'm starting with the example_single() function. I'm thinking that it would be reasonable to generate a "permanent" json file that's added to the repo, generate a dictionary from the example function, and compare it to the dictionary that's read in by json.load() on the 'permanent' file.

@martindurant thoughts?

[lsterzinger]

Also, the example_single function uses a requester pays file. Might be worth switching to a public dataset like GOES

edit: Or the NWM files used in example_multiple() since those are also anon=True