Merge branch 'bug/179' into 'master'

Serialize Checkers PluginTypeManager to a dict

*Description of changes*

Try to side-step issues with attributes not being set/updated on plugins when used with multiprocessing and Queues.

*Related to:*  #179, #164 

See merge request !98

src/flake8/processor.py

@@ -129,9 +129,9 @@ class FileProcessor(object):
 
     def update_checker_state_for(self, plugin):
         """Update the checker_state attribute for the plugin."""
-        if 'checker_state' in plugin.parameters:
+        if 'checker_state' in plugin['parameters']:
             self.checker_state = self._checker_states.setdefault(
-                plugin.name, {}
+                plugin['name'], {}
             )
 
     def next_logical_line(self):