Update ISSUE_TEMPLATE.md

Add a request for a real version number, not just "Latest"

.github/ISSUE_TEMPLATE.md

@@ -1,5 +1,6 @@
 ##### Versions
 
+*Please specify real version numbers or git SHAs, not just "Latest" since that changes fairly regularly.*
 Sarama Version:
 Kafka Version:
 Go Version: