Alias expects to expect

Allows `it { expects(subject).to eq(something) }` which is just slightly more readable than "it expect subject." It's an arguably useful change, but one that we've found nice enough to fold into our process. The same thing can be accomplished with:

```
RSpec::Matchers.module_exec do
  alias_method :expects, :expect
end
```

Apologies if I missed previous discussion about this.