Clean up the scorecard navigation

This groups similar scorecards in the nav into dropdowns by version, so we turn this:

![screen shot 2013-06-12 at 9 55 41 am](https://f.cloud.github.com/assets/1772/643158/3a3adb5a-d370-11e2-9d1a-73efce6490f3.png)

into this:

![screen shot 2013-06-12 at 9 56 26 am](https://f.cloud.github.com/assets/1772/643163/4f254e06-d370-11e2-8905-c49b69bca76b.png)

@cmeiklejohn @jgnewman @bkerley