Merge pull request #141 from MatthieuDartiailh/invoke_command_return

Make CorePlugin.invoke_action returns the value returned by the handler.

enaml/workbench/core/core_plugin.py

@@ -70,7 +70,7 @@ def invoke_command(self, command_id, parameters={}, trigger=None):
         event.parameters = parameters
         event.trigger = trigger
 
-        command.handler(event)
+        return command.handler(event)
 
     #--------------------------------------------------------------------------
     # Private API