Summary:
This adds the new default header option added in Xcode 9 B3. This works except for `//` being appended at the beginning which is referenced as a radar in the link (rdar://33451838). I used this as the default header. Let me know if you would like something else.
```/**
* Copyright (c) 2016-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*/
```
Issue fixed: #875
- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [ ] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [x] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Closes https://github.com/Instagram/IGListKit/pull/882
Differential Revision: D5611619
Pulled By: rnystrom
fbshipit-source-id: afcb11589351567eee9fea72d448cb1689153e29
