[core] Refactor -> replace some getter/setter pairs with attributes

Remove some set_* methods and replace them with a simple attribute.

see #23

tests/util.py

@@ -31,14 +31,11 @@ class MockOutput(object):
 class MockWidget(object):
     def __init__(self, text):
         self._text = text
-        self.attr_module = None
+        self.module = None
 
     def update(self, widgets):
         pass
 
-    def module(self):
-        return self.attr_module
-
     def full_text(self):
         return self._text