upgrade versioneer

Author: sappelhoff

pyprep/__init__.py

@@ -4,7 +4,6 @@
 from pyprep.prep_pipeline import PrepPipeline  # noqa: F401
 from pyprep.reference import Reference  # noqa: F401
 
-from ._version import get_versions
+from . import _version
 
-__version__ = get_versions()["version"]
-del get_versions
+__version__ = _version.get_versions()["version"]