Added warning if old files are in rendered_root

verdandi.py

@@ -61,6 +61,8 @@ class Verdandi(object):
 	def render(self):
 		if not os.path.exists(self.output_directory):
 			os.mkdir(self.output_directory)
+		if os.listdir(self.output_directory) != []:
+			print "[Warn] Ouput directory is not empty"
 		for module in self.modules:
 			module.render(self.output_directory, self.jinja_env)