More idiomatic json format

[timmahrt]

The json format exported by praatio largely mirrors the textgrids, in terms of the data that is output.

As requested on a different github project, (MontrealCorpusTools/Montreal-Forced-Aligner#453) there isn't really any need to be bound by the textgrids. We should structure the json files to be their own thing.

Details can be found in the above link.

[timmahrt]

@mmcauliffe Sorry to ping you. It's a bit late but I have a PR up with the new json format as we discussed about half a year ago 😅. If you have any concerns, please let me know. I was thinking of putting out the release next weekend or so.

[timmahrt]

I've cut a release (that includes the changes to the json format)--praatio 6.0. I opened this issue, so I'll close it now, but feel free to reopen if there any comments.

[mmcauliffe]

Awesome, thanks for this! Sorry I didn't have a chance to look over it previously, but looks good to me, I saw the PR for updating to 6.0 on conda-forge, so going to be going through MFA making sure everything's compatible.