Create a "variable" object?

[ChrisBarker-NOAA]

It would be nice to be able to get, for instance, a variable for a given timestep, and have all the attributes along with it, rather than having to query them separately (or get them in a separate object).

We could create an object that mirrors the API of a netCDF4 variable object.

We can't use the variable object itself because we only want a slice of it, and this would open the door to using the same code/API without a netcdf file at all.

-CHB