WIP es7 compliant contains

- [x] es7 polyfil for contains
- [ ] get review on the poly

--------------------------

- [ ] make enumerable stuff work correctly (ideally without lots of duplication)
- [ ] transition SHIM_ES5 to SHIM_ESNEXT

```
contains-with-nan x 1,960,211 ops/sec ±3.68% (82 runs sampled)
contains-seperate-nan x 4,872,196 ops/sec ±3.26% (80 runs sampled)
```