Changed the value passed to the substitution functions from abs to signed

Instead of passing only possitive millisecond values to string substitution
functions, now a signed millisecond value is passed.  Negative impies a future
timestamp. Postive implies a past timestamp. This might seem a little backward,
but the plugin is called "timeago" afterall.

jquery.timeago.js

@@ -57,10 +57,9 @@
           prefix = $l.prefixFromNow;
           suffix = $l.suffixFromNow;
         }
-        distanceMillis = Math.abs(distanceMillis);
       }
 
-      var seconds = distanceMillis / 1000;
+      var seconds = Math.abs(distanceMillis) / 1000;
       var minutes = seconds / 60;
       var hours = minutes / 60;
       var days = hours / 24;