Ringcentral

What's Changed
* removed accept header so to also work for binary response by DaKingKong in https://github.com/ringcentral/ringcentral-python/pull/52

New Contributors
* DaKingKong made their first contribution in https://github.com/ringcentral/ringcentral-python/pull/52

**Full Changelog**: https://github.com/ringcentral/ringcentral-python/compare/0.7.15...0.7.16

JWT tokens support

- Fixed broken Python 2.7 support
- Fixed query string arrays

- Auth Code grant
- Redirect URI support
- Custom prefixes support
- Fixed installation

- Auth Code grant
- Redirect URI support
- Custom prefixes support