User page to replace stub

[tsibley]

When logged in, clicking on your username in the top right nav leads to a very bare bones page that includes the list of groups you're in and a logout link. This was due to time constraints during initial implementation. We'd like to replace this with a user page that fits in with the rest of the site. To start with, it doesn't have to have any more content then it currently does. I think the URL should change from /whoami to /users/<name>. (The /whoami API endpoint still needs to stay for the client.)

[jameshadfield]

Closed by #71