_.bind supports _.partial application, but not its non pre-filled argument syntax with _

Nobody has claimed this yet.

I don't know if this is intended behavior, but it seems all around confusing if so. My guess is this portion of _.bind was just left untouched when _.partial received this functionality. Here's the simplified reproduction of it in jsfiddle: http://jsfiddle.net/j3jpL4eb/1/

``` javascript
var foo = function(bar) {
console.log(bar); //this should always print 'bar' if non pre-filled arguments applied to bind's partial application as well, yet it has the value of underscore when not double wrapped
}

_.bind(foo, this, _)('bar'); //function (n){return n instanceof m?n:this instanceof m?void(this._wrapped=n):new m(n)}
_.bind(_.partial(foo, _), this)('bar'); //bar
```

Start by running the JavaScript reproduction from the issue and compare _.bind(foo, this, _)('bar') with the _.partial-wrapped example. Inspect the _.bind and _.partial entry points to determine whether underscore placeholders should be handled consistently; done means the direct bind form passes 'bar' to foo like the wrapped form.

Written by the indexing model from the issue text.