Move the UI showing the time left into its own component.

This also fixes (at least in part) the undesired full re-render of the whole modal.

Close #10.
Disallow closing the Question modal before answering all the questions.

See #13.
Fix missing key.
Tile.won => Tile.wonBy.
Disable link on disabled tiles.
Render question modal fullscreen.

See #13.
Show close button on time up.