Add clone option

Adds new opts parameter, for opting out of cloning.

Before

```sh
$ make bench

                      Facade
         104,837 op/s » new Facade()
         653,505 op/s » .proxy
         422,273 op/s » .field

  Suites:  1
  Benches: 3
  Elapsed: 4,122.18 ms
```

After

```sh
$ make bench

                      Facade
         111,908 op/s » new Facade()
         931,917 op/s » .proxy
      98,616,373 op/s » .field


  Suites:  1
  Benches: 3
  Elapsed: 4,050.08 ms
```

Woot. @calvinfo