add json lightcurves to example files

[tylerbarna]

Feature Summary
We have a handful of lightcurve files that are in dat format, would be good to have a few that are also in the nmma-compatible json format

Implementation details
Generate some json lightcurves and add to example lightcurves. Maybe have any relevant io tests also run on a json file to make sure compatibility isn't broken when making changes to analysis and the like