Tab
===

Switch between panels.

The panel currently in use has its border colorized.

Some actions are possible only if the right panel is selected. For example, if
you want to add a task in the todo list, you need first to press the 'TAB' key
to get the todo panel selected. Then you can press 'a' to add your item.

Notice that at the bottom of the screen the list of possible actions change
while pressing 'TAB', so you always know what action can be performed on the
selected panel.
