Minor stuff, cleanup and formating.

bonobo/plugins.py

@@ -0,0 +1,23 @@
+class Plugin:
+    """
+    A plugin is an extension to the core behavior of bonobo. If you're writing transformations, you should not need
+    to use this interface.
+    
+    For examples, you can read bonobo.ext.console.ConsoleOutputPlugin, or bonobo.ext.jupyter.JupyterOutputPlugin that
+    respectively permits an interactive output on an ANSI console and a rich output in a jupyter notebook.
+    
+    Warning: THE PLUGIN API IS PRE-ALPHA AND WILL EVOLVE BEFORE 1.0, DO NOT RELY ON IT BEING STABLE!
+    
+    """
+
+    def __init__(self, context):
+        self.context = context
+
+    def initialize(self):
+        pass
+
+    def run(self):
+        pass
+
+    def finalize(self):
+        pass