Set grib2io as a dependency

[TimothyCera-NOAA]

No description provided.

[EricEngle-NOAA]

What was the rationale for having grib2io as a dependency? I know it makes sense...but just wondering.

[TimothyCera-NOAA]

I don't recall any other reason than that you can't use grib2io-interp without grib2io. I think if someone sees grib2io-interp first they might think, "This is the interpolation version of grib2io" and just install grib2io-interp. With this dependency they would actually get the interpolation version of grib2io. That's all I got.

[EricEngle-NOAA]

Technically grib2io is not required. If you had the appropriate GRIB2 grid definition information at hand, you can just all that an source grid into the interpolation subroutines, but even in the README, it states that one should use the grib2io.interpolate function.

So lets get this in then. Eventually grib2io and grib2io-interp will come back together anyways.