fixing typos (possessive case)

remotes/index.html

@@ -307,7 +307,7 @@ To git@github.com:schacon/hw.git
     at the same time, you both do commits, then she pushes and then you try to
     push, Git will by default not allow you to overwrite her changes.  Instead,
     it basically runs <code>git log</code> on the branch you're trying to push and
-    makes sure it can see the current tip of the servers branch in your pushes
+    makes sure it can see the current tip of the server's branch in your push's
     history.  If it can't see what is on the server in your history, it concludes
     that you are out of date and will reject your push.  You will rightly have to
     fetch, merge then push again - which makes sure you take her changes into