add an example of docker ps, and also of link aliases

a question from irc prompted me to add a little more info :)

@metalivedev

```
<jjjjjosh> does anyone know why, when you do `docker ps` the column is called "names" and not "name"?
<jjjjjosh> i'm mostly curious
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<jjjjjosh> i tried doing `sudo docker run -d -name foo -name bar ubuntu /bin/sh -c "while true; do echo Hello world; sleep 1; done"`
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<jjjjjosh> and it just takes the last name (so, "bar")
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<jamesottaway> if you spawn another container and link it to the first, you'll see another name on the first container
<jamesottaway> so spawn foo, then spawn bar and link to foo
<jamesottaway> the names for foo will be 'foo' and 'bar/foo'
<jjjjjosh> awesome thanks!
```

<div class="discussion-labels">doc</div>