add recipe for bbdb-

bbdb-.el requires bbdb.el.
But I'm not sure of the format of the latest version of bbdb.el.
I'd written the following line in bbdb-.el.

```lisp
;; Package-Requires: ((bbdb "20140123.1541") (log4e "0.2.0") (yaxception "0.1"))
```

It this format OK?

Best regards.