Adding link to stackoverflow source

Change-Id: Iedd3e300db97ccbab3991480ed269799251e0874
diff --git a/voltha b/voltha
index ceb9154..6eccbeb 100755
--- a/voltha
+++ b/voltha
@@ -205,6 +205,7 @@
 }
 
 # returns the greater version (0 if equal)
+# inspired by https://stackoverflow.com/questions/4023830/how-to-compare-two-strings-in-dot-separated-version-format-in-bash
 function semvercompare() {
     if [[ "$1" == "$2" ]]
     then