404 on authorize

[sweetcoco]

looks like fitbit's OAuth 2.0: Authorization URI is: https://www.fitbit.com/oauth2/authorize

the config file here sets the base url to:

const FITBIT_BASE_API_URL = 'https://api.fitbit.com';

causing a 404 when attempting to authorize.

[guumaster]

They've changed it to the new url. I'll update it soon, or accept a PR.