Add documentation regarding http keep-alive issue
* [Health Checks](misc/health_checks.md)
* [Monitoring](misc/monitoring.md)
* [Tracing](misc/tracing.md)
+* Known Issues
+ * [Stale HTTP Keep-Alive](misc/http_keepalive.md)
* Upgrade Notes
* [2.x to 3.x](upgrade/3x.md)
* [3.6.x to 3.7.x](upgrade/3.7.x.md)
