Dispense with View#options merging.

As discussed in #2458, using defaults is unnecessary when attaching options directly to new instances.

For example, this code

```js
var View = Backbone.View.extend({
  options: {
    foo: 15,
    bar: false
  },
  initialize: function(options) {
    _.extend(this, _.pick(options, 'foo', 'bar'));
  }
});
```

is better written as and functionally equivalent to

```js
var View = Backbone.View.extend({
  foo: 15,
  bar: false,
  initialize: function(options) {
    _.extend(this, _.pick(options, 'foo', 'bar'));
  }
});
```

With that in mind, there is really no need for merging options with `View#options`.