Move language and versions into top menus.

Based on #459 I've moved the language nav to the header and made it a dropdown menu.  I've also made the versions list a dropdown. I also make the menus accessible via keyboard  as I hate using a mouse, and figured others probably do too.

It looks like this when one of the menus is open 
![Screen Shot 2013-03-22 at 10 32 24 PM](https://f.cloud.github.com/assets/24086/293422/6e792f26-9364-11e2-8a26-70c589d4cab0.png)