Events capturing when models are re-selected

[hashchange]

Here are some of new events, triggered when models are re-selected:

• reselected (model),
• reselect:one (single-select collection),
• reselect:any (multi-select collection).

The PR is based on #23 (support for model sharing across collections).

There also is a change in the spec: selectAll and deselectAll no longer fire events when they are a no-op. This had been inconsistent with the behaviour of select, which does not trigger an event unless the selection is actually changed.

Tests and documentation are included.