s/username/user-name/ to please htmlproofer

Author: OlivierBlanvillain

contribute/hacker-guide.md

@@ -67,7 +67,7 @@ If you're new to Git, don't be afraid of messing up-- there is no way you can co
 
 ### Clone
 
-If everything went okay, you will be redirected to your own fork at `https://github.com/username/scala`, where `username`
+If everything went okay, you will be redirected to your own fork at `https://github.com/user-name/scala`, where `username`
 is your github user name. You might find it helpful to read [http://help.github.com/fork-a-repo/](http://help.github.com/fork-a-repo/),
 which covers some of the things that will follow below. Then, _clone_ your repository (i.e. pull a copy from GitHub to your local machine) by running the following on the command line: