Let ScrollSpy support uri encoded hash fragments

The updated line threw a syntax error when an encoded fragment is given.

```js
href = encodeURIComponent('#テスト')
$(href)
// Error: Syntax error, unrecognized expression: %23%E3%83%86%E3%82%B9%E3%83%88
```

And browsers (at least Chrome 37.0.2062.124 and Firefox 32.0.3) automatically encodes `a[href]` values due to rfc3986:

```html
<!-- server response -->
<a href="#テスト"></a>
<div id="テスト"></div>

<!-- browser recognizes as -->
<a href="#%23%E3%83%86%E3%82%B9%E3%83%88"></a>
<div id="テスト"></div>
```

This means that there is no way to use the plugin with non-ascii hash fragments. This PR fixes the problem.

Patched script works fine on my pages, however, I'm afraid of breaking something important because I'm not familiar with such encoding problems :fearful:  
Thanks.
See https://github.com/twbs/bootstrap/commit/61705d35fa314a16579169fb7379e5101716e715, thanks for pointing it out!