adding gridmarthe package

[manlaya]

Adding gridmarthe python package (and using fortran librairie with f2py)

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[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/gridmarthe/meta.yaml) and found it was in an excellent condition.

[manlaya]

Tests checks, ok for review :)
python package with a fortran src, so
@conda-forge/help-python-c
(not quite sure of the tag...)