Fix error when creating a new spec.

`SwitchCommand#snippet` failed when the bundle was installed via TextMate’s bundle preferences because the snippet files then use binary property list format (see https://github.com/rspec/rspec-tmbundle/issues/92#issuecomment-58075684 for details).

However, the method's return value was discarded anyway :-/ (In b48e860171f548 `#write_and_open` was changed to ignore the `content` parameter.)

This commit removes all the unused code (at least I hope so).