Get failing example to actually fail

Turns out you need to _return_ the promise for mocha to pick up on the
asynchronous assertions.
Fix failing test

Now that we're not getting a false positive, we can write a good
example test.
Bump gozer version

So we can actually use it without having to install phantomjs ourselves
Remove unneeded dependencies

We never needed express, and we can remove coffee-script now that gozer
is straight JS.

Setting a timeout of 3s, since the tests occasionally take that long.