changed to RSpec's expect syntax

I decided to change clearance to expect syntax for a project I was working on.  If, you want what I did, great!  If, not, you can just close this.

Please note, I have not done a poll request before.  If I have done it incorrectly, I apologize.
I'd probably extract a variable to run the expectation against:

```
request = request_with_remember_token(user.remember_token)

expect(signed_in_constraint.matches?(request)).to be_truthy
```