login() doesn't support redux-saga call effect

[peteroid]

Hi maintainer, thanks for the great effort on making this nice library.

I found that the method call of login doesn't work in the following scenario.

// this doesn't work
// the error message is about this.getUserInfo being undefined
const tryLogin = function * () {
  const user = yield call(SnapchatKit.Login)
}

// this works
const tryLogin = function * () {
  const user = yield SnapchatKit.Login()
}

I believe this behavior has been discussed in redux-saga/redux-saga#27.

I suggest we can make a use of the arrow function to define the class method as suggested in the issue.

[mduthey]

I will take a look when I have some of time :) Do you have some dummy project where I can test?

Thanks!