Replace refute + positive capabara matcher in cucumber steps

In general it's a bad idea to use patterns like the following with Capybara:
```
refute page.has_content? "something"
```

With most of Capybara's matchers, it'll wait around a bit and try
again if the matcher returns false. Capybara does this to support
Javascripty / AJAXy stuff, but it can cause unnecessary delays (regardless of
driver).

Capybara provides negative versions of all it's matchers, so something like this 
is the way to go:
```
assert page.has_no_content? "something"' 
```

This commit changes 27 instances of the negative pattern in cucumber steps,
and that small change shaves nearly 15 secs off the test run.