Fix 400 error on mfa authentication

[k3an3]

The web API uses device_token as one of the fields during authentication. Looking at the issues for this and other similar API clients, people have been generating these randomly but it can also be done by the standard uuid library.

Without this change, I get this error calling Client.authenticate():
requests.exceptions.HTTPError: 400 Client Error: Bad Request for url: https://api.robinhood.com/oauth2/token/

Second, the API also takes a nonzero parameter when fetching all options positions. Thought it was nice to include this since you don't get as much garbage data this way. Could even make this the default option if so inclined.

[westonplatter]

Thanks @k3an3 for the PR.

What kind of garbage data is excluded?

[k3an3]

If you don't include nonzero=True, the positions returned includes (all?) historic options positions where the quantity == 0. So if I run it the default way, I get my current open positions (which is only a few entries), and then basically every single other position I've ever had. It seems slower to pull all of this data, and I don't think it is necessary unless you are specifically trying to go back and look at all of your historic options. This fix just saves you from filtering by positions with quantity != 0

[wardnath]

I've found that I need to include X-ROBINHOOD-CHALLENGE-RESPONSE-ID to the headers to resolve the 400 issue.

see: robinhood-unofficial/pyrh#176 (comment)

[westonplatter]

@k3an3 @wardnath I moved authentication operations into a new library, fast_arrow_auth. I used your code changes to help figure out how handle the device token there (THANKS!!). What I'm thinking is make update this PR to only contain the nonzero logic.

[westonplatter]

@k3an3 I pull in your option position changes into #97 and resolved the merge conflicts there. I'll wait a couple of days in case you had thoughts or feedback on how I adjusted the code changes.

Thanks a ton for your help on removing garbage data from the options position code.

[westonplatter]

@k3an3 I went ahead and merged #97 with your option position API changes.