Bugfix initial collection events not being re-bound when re-rendered.

This pull request fixes #714

CollectionView does not start listening to collection events again after being closed and re-rendered.

Bug:
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Reproduce:
1) http://jsfiddle.net/tUwVy/2/
2) Click add a few times
3) Click close
4) Click open
5) Click add a few more times.

CollectionView does not start listening to collection events again after being closed (`stopListening`) and re-rendered.

Calling internal method CollectionView#_initialEvents will rebind them again.

Proposed Solution:
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1 Set _initialEventsBound to true immediately after calling _initialEvents in the constructor
2. Set _initialEventsBound to false when closing
3. If _initialEventsBound is false when rendering, invoke _initialEvents again.

Alternate Solution:
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Could instead call a public `reinitialized` method from Region#show if the previous view was closed.
`reinitialized` would then call the `_initialEvents` internal method.

I don't like that solution as much as it would require you to be using a layout vs. this working natively when just re-rendering.