ssl_exporter upstream release - 2.1.0
ssl_exporter upstream release - 2.1.0

Bump to 2.1.0
---
c0f4183 release 2.1.0
17aa4e2 Add metrics for certificates in the verified chains (#48)
ddedd5f Add more information to error logs (#49)
ac9bc31 add a file name extension to the generated binary when the host (e.g. windows) requires it (#47)
b4b8471 build windows release (#43)
lest/prometheus-rpm,lest/prometheus-rpm