Make point editable in zoom view only.

![screen shot 2014-09-28 at 12 04 50 pm](https://cloud.githubusercontent.com/assets/1187682/4461325/7bc085b0-48b9-11e4-8178-40954f18095c.png)

When the overview is sufficiently sized, the handle appears, but is not veritically centered to height. We think that it's also clutter to have the the drag handle in both places. This change makes points only editable in the zoom view.

Note: The demo commit can be omitted, as it only changes the height of the overview in the index.html
It is an elegant way of doing the check - although I'd like not to introduce unnecessary dependency in the component — more than the existing ones.

The same check could be done with `view === peaks.waveformZoomView`.

Ideally in the future there will be only one view object, configurable with its own options — the marker ones definitely fit in.