Change C, D and Y to be in line with paredit-kill

In situations like this:

```cl
(progn
  (foo)
 |(bar (baz)))
```

paredit-kill lets use kill to get:
   ```cl
(progn
  (foo)
 |)
```
With this in mind, C, D and Y now does what you'd expect.  See the individual commit messages for examples.