Only add running class if it isn't already present

Author: zackbloom

pace.coffee

@@ -203,7 +203,8 @@ class Bar
       @el.className = "pace pace-active"
 
       document.body.className = document.body.className.replace /pace-done/g, ''
-      document.body.className += ' pace-running'
+      if not /pace-running/.test document.body.className
+        document.body.className += ' pace-running'
 
       @el.innerHTML = '''
       <div class="pace-progress">