[core/input] Separate module/widget update and retrieval

To make it easier to update individual modules, separate the call to
update() and the call to actually drawing the status.

Additionally, this avoids the "side effect" of updating when drawing the
status line.

core/output.py

@@ -5,7 +5,7 @@ import time
 class i3(object):
     def __init__(self):
         self._modules = []
-        self._status = []
+        self._status = {}
 
     def modules(self, modules=None):
         if not modules:
@@ -31,20 +31,23 @@ class i3(object):
     def stop(self):
         return { 'suffix': '\n]' }
 
-    def patch(self, affected_modules):
-        pass # TODO
-
-    def statusline(self):
-        self._status = []
+    def update(self, affected_modules=None):
         for module in self._modules:
+            module.update()
+            self._status[module] = []
             for widget in module.widgets():
-                self._status.append({
+                self._status[module].append({
                     'full_text': widget.full_text(),
                     'instance': widget.id(),
                     'name': module.id(),
                 })
+
+    def statusline(self):
+        widgets = []
+        for module in self._modules:
+            widgets += self._status[module]
         return {
-            'data': self._status,
+            'data': widgets,
             'suffix': ','
         }