fix: Clean out dist and build before building

This should fix the problem with uploading old versions.

Fixes #86

semantic_release/pypi.py

@@ -21,6 +21,7 @@ def upload_to_pypi(
     """
     if username is None or password is None or username == "" or password == "":
         raise ImproperConfigurationError('Missing credentials for uploading')
+    run('rm -rf build dist')
     run('python setup.py {}'.format(dists))
     run(
         'twine upload -u {} -p {} {} {}'.format(