Fix small issues for publishing on PyPI (#88)

setup.cfg

@@ -1,9 +1,6 @@
 [metadata]
 name = pyqmix
-author =
-    Lorenzo Alfine <[email protected]>
-    Richard Höchenberger <[email protected]>
-    Camilla Arndal Andersen <[email protected]>
+author = Lorenzo Alfine <[email protected]>, Richard Höchenberger <[email protected]>, Camilla Arndal Andersen <[email protected]>
 author_email = [email protected]
 url = https://pyqmix.readthedocs.io/
 project_urls =
@@ -13,6 +10,7 @@ license = GPL v3
 license_file = LICENSE
 description = A wrapper for the Cetoni Qmix SDK.
 long_description = file: README.md, CHANGES.md
+long_description_content_type = text/markdown
 classifiers =
     Intended Audience :: Science/Research
     Programming Language :: Python