Fix docstring

guessit/rules/__init__.py

@@ -72,6 +72,9 @@ def rebulk_builder():
     rebulk.rebulk(type_())
 
     def customize_properties(properties):
+        """
+        Customize default rebulk properties
+        """
         count = properties['count']
         del properties['count']
 

guessit/rules/properties/mimetype.py

@@ -42,4 +42,7 @@ class Mimetype(CustomRule):
 
     @property
     def properties(self):
+        """
+        Properties for this rule.
+        """
         return {'mimetype': [None]}