Search bar should take all width when no select is alongside (when just one crate is documented)

A good screenshot:

<img width="826" alt="Screenshot 2019-05-02 at 21 57 35" src="https://user-images.githubusercontent.com/3050060/57103257-973bb180-6d25-11e9-8dab-a79fc56f3afd.png">
