Merge pull request #103 from spacetelescope/license-file-kwd

Updating deprecated license_file kwd

Author: jaymedina

setup.cfg

@@ -3,7 +3,7 @@ name = astrocut
 author = MAST Archive Developers
 author_email = archive@stsci.edu
 license = BSD 3-Clause
-license_file = licenses/LICENSE.rst
+license_files = licenses/LICENSE.rst
 url = https://astrocut.readthedocs.io
 description = Cutout tools for astronomical images
 long_description = file: README.rst