Migrated Dropbox endpoints to use v2

[adamo57]

• Updates endpoints to point to the v2 of the Dropbox API

Fixes #204

[bentranter]

Hey @adamo57, thanks for the PR! Looks like Dropbox might've made another change, as when I try to run this, everything works until the point where it tries to get the user in the FetchUser function in dropbox.go.

It seems like Dropbox now requires a POST request for that endpoint, so if you could change https://github.com/adamo57/goth/blob/adamo57-migrate-dropbox-endpoint/providers/dropbox/dropbox.go#L90 to use a POST request instead of the current GET, then I believe that should fix this.

[bentranter]

Dropbox requires a POST request to the users/get_current_account endpoint now, see the other comment I made for more info.

[adamo57]

@bentranter mind taking a peek again please?

[bentranter]

Awesome, works for me now. Thanks for this!