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.
```ruby
headers.should set_cookie('remember_token',
                                            user.remember_token,
                                            remembered_expires)
```