Add Polls field to Tweet Entities
Add Polls field to Tweet Entities

* Add PollEntity and PollOption types

Close #168

Co-authored-by: solaxun <f0acc0cc548150c126d02df5a58eb97d3bf3ee5a@gmail.com>
Co-authored-by: Dalton Hubble <9ee58f02bdc3563affdf4161c512c2d8a7a211c3@gmail.com>

dghubble/go-twitter