Add Stackoverflow yaml-cpp tag URL to the README (#474)

Author: devnoname120

README.md

@@ -6,7 +6,7 @@ To get a feel for how it can be used, see the [Tutorial](https://github.com/jbed
 
 # Problems? #
 
-If you find a bug, post an [issue](https://github.com/jbeder/yaml-cpp/issues)! If you have questions about how to use yaml-cpp, please post it on http://stackoverflow.com and tag it `yaml-cpp`.
+If you find a bug, post an [issue](https://github.com/jbeder/yaml-cpp/issues)! If you have questions about how to use yaml-cpp, please post it on http://stackoverflow.com and tag it [`yaml-cpp`](http://stackoverflow.com/questions/tagged/yaml-cpp).
 
 # How to Build #