Release 0.21.1

Signed-off-by: Chris Marchbanks <csmarchbanks@gmail.com>

Author: csmarchbanks

setup.py

@@ -8,7 +8,7 @@
 
 setup(
     name="prometheus_client",
-    version="0.21.0",
+    version="0.21.1",
     author="Brian Brazil",
     author_email="brian.brazil@robustperception.io",
     description="Python client for the Prometheus monitoring system.",