We need to add the "complete" method to the Interpreter/Engine/Controller in IPython1

[Brian Granger]

The Interpreter class in ipython1.core.interpreter should have a complete method that take a string and returns a valid list of completions. For now, this can just raise NotImplementedError. This method will also need to be added to the various Engine/Controller interfaces and implementations. This is needed so frontend writers can begin to call the method.