* v0.2

This version mainly introduces some facilities to place common
components on the panes. These components are not mandatory and can
happily be ignored. They are all hidden by default.

- A header message, packed to the top of the pane, aims at providing
  indications or help on the current pane activity or inputs.

- An error message, packed at the bottom of the pane, to signal some
  contextual event, like the necessity to fill some input, an error
  which occured during a background task, and so on.

- A progress bar in ActivePane instances, packed just above the
  error message.

A pane now can also clear itself. See `git log' for other fixes.