test suite should test json files

[ocehugo]

Currently the run_tests.sh script is not testing the output of ncdump-json, just if the command should run.

I also believe that more cdls can be add to the testing suite (unidata has a lot of them). I think the best way to handle this is a list of the file locations (or http locations) so you could load the file, run ncdump-json in all entries, and test a json reader on the output.

Cheers

[jllodra]

Hi @ocehugo,

tests were done, but I switched to python json.tool, added a new unidata example file, and improved the tests/README.md to make things clear.

Thank you