add gravatar plugin and pelican_generate_context signal

plugins_samples/gravatar.py

@@ -0,0 +1,20 @@
+import hashlib
+
+from blinker import signal
+
+
+def add_gravatar(generator, metadatas):
+    
+    #first check email
+    if 'email' not in metadatas.keys()\
+        and 'AUTHOR_EMAIL' in generator.settings.keys():
+            metadatas['email'] = generator.settings['AUTHOR_EMAIL']
+            
+    #then add gravatar url
+    if 'email' in metadatas.keys():
+        gravatar_url = "http://www.gravatar.com/avatar/" + \
+                        hashlib.md5(metadatas['email'].lower()).hexdigest()
+        metadatas["author_gravatar"] = gravatar_url
+    
+    
+signal('pelican_generate_context').connect(add_gravatar)