Make sure temp files are removed

[emfdavid]

Change temp file behavior to ensure files are unlinked (removed).
Related to #283

[FussyDuck]

All committers have signed the CLA.

[iainrussell]

Hi @emfdavid,

Many thanks for taking an interest in cfgrib and for contributing a change!

But in fact these files are not temporary, they are index files that persist on the filesystem in order to avoid potentially expensive re-scanning of a GRIB file each time it is opened.

However, you can suppress their creation completely by passing the indexpath argument to cfgrib like this:

xr.open_dataset('era5-levels-members.grib', engine='cfgrib', backend_kwargs={'indexpath':''})

Best regards,
Iain

[emfdavid]

Closing per discussion in #283