SelectView should work properly with optionValuePath and selection

SelectView was not working property when `optionValuePath` and `selection` properties were set. 
`selection` and `value` properties did not update, also `selected` attribute was not set on option tag. 

Typical use case in which SelectView content was bound to ember-data records array and selection was bound to some ember-data object fail to set Select into proper state. Example: http://emberjs.jsbin.com/zemomorunu/1/

This PR aims to improve SelectView so its content can be bound to array of any Ember objects.

TODO:
* support for `multiple=true`
`Ember.Select` is already setting a default `optionLabelPath` (see [here](https://github.com/chrmod/ember.js/blob/select-value-path-fixes/packages/ember-handlebars/lib/controls/select.js#L433)) so I don't think we need to use `getWithDefault` here.

Is there something I am missing on that?