implemented github activity plugin

pelican/utils.py

@@ -222,3 +222,15 @@ def files_changed(path, extensions):
         LAST_MTIME = mtime
         return True
     return False
+
+def singleton(cls):
+    """
+        Singleton decorator for multiple calls inside plugins
+        for an example see pelican/plugins/github_activity.py
+    """
+    instances = {}
+    def getinstance(*args, **kwargs):
+        if cls not in instances:
+            instances[cls] = cls(*args, **kwargs)
+        return instances[cls]
+    return getinstance