Originally filed as http://www.reinteract.org/trac/ticket/70

After you insert the completion to a function, we currently put you between a set of empty parentheses to type arguments, then you have to cursor over the end parenthesis which is annoying.

Simple:

    Draw a box around whatever the user types to indicate an argument entry mode, and when the user hits return, jump out of the mode and move the insert after the close parenthesis

Complex:

    Same thing, but use doc string information where available to show a name for each argument, and make return take you to the next return. If there are keyword arguments, then put , [] after the last argument and let the user enter additional stuff, or hit Return immediately to remove the comma.