Prepopulate snippet description in tweet share

Author: rossta

app/views/share/snippet_tweets/tweet_button.rb

@@ -28,7 +28,7 @@ def share_url
   end
 
   def tweet_text
-    "Created with @joyofrails #{share_url}"
+    [@snippet.description.presence, "Created with @joyofrails #{share_url}"].compact.join("\n\n")
   end
 
   def encode(text)