Fetch a Twitter api access token in using a generator function.

get-twitter-token.js

function *getToken () {
  let options = {
        'auth': {
          'user': appConsumerKey,
          'pass': appConsumerSecret,
          'sendImmediately': true
        },
        'form': {
          'grant_type': 'client_credentials'
        }
      },
      response = yield post(tokenUrl, options);
  return parse(response.body).access_token;
}