Update readme and tests

[mccalluc]

• fix Make the example in the README a doctest #1
• fix Test across a range of opendp versions #2
• fix "logging" or "logger"? #3
• fix Update opendp import #4
• fix Code coverage? #8

I think my next step would be to add a schema.

• JSON Schema? #5

If we may be assembling these structures by hand, it's nice to have early feedback that we're missing something, rather than an error from deeper in the code... but if the structure is particularly complex, maintaining it might not be worth the effort. Thoughts?

[Shoeboxam]

Thanks, looks like a good update.