Authentication to Github should use Authorization HTTP header

[cwjohnston]

I've started receiving emails from Github indicating that Bonsai is using a deprecated mechanism to authenticate to GitHub's User API:

Hello there!

On February 7th, 2020 at 19:11 (UTC) your application (Bonsai) used an access token (with the User-Agent Faraday v0.15.4) as part of a query parameter to access an endpoint through the GitHub API.

https://api.github.com/user

Please use the Authorization HTTP header instead as using the `access_token` query parameter is deprecated and will be removed July 1st, 2020.

Depending on your API usage, we'll be sending you this email reminder once every 3 days.

Visit https://developer.github.com/changes/2019-11-05-deprecated-passwords-and-authorizations-api/#authenticating-using-query-parameters for more information.

Thanks,
The GitHub Team 

We should update the application to use the indicated HTTP header instead of query parameters.