v1.1.8

Another minor update to address issues arising from running with GEOS IT.

1. Download URLs for GEOS IT updated to latest product.
2. Solves an issue running the satellite interface (oco, gosat, or geocarb subcommands)
   with 3 GEOS IT input. The interpolators created for the GEOS IT files are large enough that
   three cannot be passed between threads in Python 3.6 due to a limit on the number of bytes
   that the Python 3.6 multiprocessing module can pickle. This is fixed by Python 3.10 at the
   latest, but getting Python 3.10 and required numerical dependencies to reproduce the Python
   3.6 results to numerical precision was not possible. Therefore, as a workaround, if the
   satellite interface detects that it is running on Python 3.9 or earlier, it will pickle the
   interpolators as separate files and load them back in from the threads when --nprocs is not
   0.

There are two other aspects to this release:

1. This is the first release that can be run on Python 3.10 and has the changes needed to run
   the satellite interface with GEOS IT files. v1.1.7 didn't have those GEOS IT changes and
   v1.1.5d was not compatible with Python 3.6.
2. The unit testing code now ignores the GINPUT_VERSION value in the .vmr file headers; this
   saves us from needing to update the test input files with each version if there should not
   be changes in the output.