These doc strings aren't very descriptive, and produce doc output like:

```` ruby
expect(...).to ~(matcher)
  can pass
  can pass
  can pass
```

Would be good to use more specific doc strings, such as `it "can pass when using ~"`, `it "can pass when using !"`, etc.

Also, I don't see any examples that show that it can properly fail, too -- as things stand now, I think things would pass if the implementation of the matcher was simply `true`.