A new Component and Container is introduced: Modal.
It dispatches an UNSELECT_ALBUM action when clicked on.
Some CSS is added to bur out the background and display the modal
content properly.
React app with Redux state, mostly based around the todo example in the
Redux documentation.
It's a list of items (albums) which can be filtered by a string.
* A list of albums that is mapped from state to props.
* A filter input is controlled by redux state.
