Features
- [twitch] add helix channel API methods (474e9fe, #135)
- [twitch] add helix tags & search API methods (6021b7e, #135)
- [twitch] add commercial & stream key API methods (e1dd435, #135)
- [twitch] add follow create/delete API methods (2ce5206, #135)
- [twitch] add cheermotes resource to Helix bits API (23d2bff, #135)