bump version to 0.2.1

Author: Zsailer

jupyter_server/_version.py

@@ -9,5 +9,5 @@
 
 # Next beta/alpha/rc release: The version number for beta is X.Y.ZbN **without dots**.
 
-version_info = (0, 3, 0, '.dev')
+version_info = (0, 2, 1, '')
 __version__ = '.'.join(map(str, version_info[:3])) + ''.join(version_info[3:])