fix(ischanged) first argument in callback: error

lib/server/ischanged.js

@@ -17,6 +17,8 @@
     exports.isFileChanged = function(name, callback) {
         var readTime = Times[name];
         
+        Util.checkArgs(arguments, ['name', 'callback']);
+        
         time.get(name, 'raw', function(error, fileTime) {
             var json, timeChanged;
             
@@ -30,7 +32,7 @@
                 writeFile(CHANGES_JSON, json);
             }
             
-            Util.exec(callback, timeChanged);
+            callback(error, timeChanged);
         });
     };