Display user's full name in header link

We're recording users' full names but aren't showing it to them in the header.  This pull request remedies this.

Manual testing
---------------
 1. Sign in as **root**
 2. Edit the profile and set the "Full Name" field to **I am root**
 3. Sign out.
 4. Sign in as **root** again.
 5. Look in the header: ![i am root](https://f.cloud.github.com/assets/297515/2348259/c611fe58-a555-11e3-8a2f-5792fcc92d00.png)

Mission accomplished!