Clicking on the Discourse header logo scroll back to top in homepage

When on the homepage, and you click on the Discourse logo, you're now taken to the top of the browser. As per [this request](http://meta.discourse.org/t/discourse-logo-link-back-to-top-of-thread-list-on-home-page/3592/2).

**Note:** I did not add a _touchstart_ bind to the logo because it then fires twice. This got me wondering about the other bindings using both -- here is one example

```
this.$('a[data-dropdown]').on('click touchstart', function(e) {
        return _this.showDropdown(jQuery(e.currentTarget));
      });
```

Doing both then results in the callback function being fired twice, when tapping on an iPad. I'm not sure if this is a concern for you guys.