Add warning to splashdot recipe about IP banning

resources/recipes/slashdot.recipe

@@ -9,6 +9,8 @@ from calibre.web.feeds.news import BasicNewsRecipe
 
 class Slashdot(BasicNewsRecipe):
              title          = u'Slashdot.org'
+             description    = '''Tech news. WARNING: This recipe downloads a lot
+             of content and can result in your IP being banned from slashdot.org'''
              oldest_article = 7
              max_articles_per_feed = 100
              language = 'en'