Use a greedier regex for updating users

Right now, updating a user's field regexes on word characters, so `@` and `.` don't work.  This means updating email addresses or jabber ids doesn't work.

Specifically, trying to do this fails with the current regex:
```
jarvis update user 123456 jid 12345_123456@chat.hipchat.com
```

Tagging @Drewzar for reivew.