Update CONTRIBUTING.md

CONTRIBUTING.md

@@ -1,6 +1,6 @@
 
 # Stack Overflow
-**Stack Overflow** is a fantastic resource for programmers, with many active users who are usually able to answer questions much quicker than I can. 
+**Stack Overflow** is a fantastic resource for programmers, with many active users who are usually able to answer questions much quicker than I can. Tag then with `reachability-swift`
 
 [Follow this link](http://stackoverflow.com/questions/ask?tags=reachability-swift) to ask your question on SO