Fix Graphical Error on Admin Dashboard

When clicking on a subsection of the Users section of the admin dashboard, the "Users" link loses its active state.

![screen shot 2013-07-18 at 11 28 10 pm](https://f.cloud.github.com/assets/860486/823833/881aa57e-f023-11e2-8ba3-75ff9b1f559e.png)

Compare this to the Email section, which works properly:

![screen shot 2013-07-18 at 11 33 21 pm](https://f.cloud.github.com/assets/860486/823838/fe7e5ba2-f023-11e2-8f74-aea8c12fe78a.png)


This is because the "active" route is specifically linked to.  Compare the following, from `app/assets/javascripts/admin/templates/admin.js.handlebars`:
```
<li>{{#linkTo 'adminUsersList.active'}}{{i18n admin.users.title}}{{/linkTo}}</li>
...
<li>{{#linkTo 'adminEmail'}}{{i18n admin.email.title}}{{/linkTo}}</li>
```

To resolve this, I am redirecting to the "default" page instead of linking directly to it.  Flags has the same issue and was correctly similarly.

Feedback welcome, thanks!