Allow the user cycle between available alternatives with arrow keys or tab

[dlight]

If I press the arrow key down or press TAB, icepick should cycle between the alternatives shown. Currently, it always selects the first alternative, and it tries to process arrow keys and tab as regular input (adding it to the buffer).

With this modification, after an arrow key as pressed icepick would still remember the buffer the user filled, and would resume filling the buffer if another key is pressed, cancelling the cycling (unless the selected line is still shown, then it keeps it selected). Also a key like C-g or ESC could cancel cycling and go back to select the first element.