Update versioneer

No more pyop2-unknown

Author: wence-

pyop2/__init__.py

@@ -10,5 +10,5 @@
 from version import __version__ as ver, __version_info__  # noqa: just expose
 
 from ._version import get_versions
-__version__ = get_versions(default={"version": ver, "full": ""})['version']
+__version__ = get_versions()['version']
 del get_versions