Remove un-needed access_token in Resource Owner Details URL
Remove un-needed access_token in Resource Owner Details URL

Was getting the following error with it in, not sure if this was a Dropbox API change or the way The League OAuth client handles requests.

Cannot specify both an "Authorization" header and the URL/POST parameter "access_token".

Closes #6
stevenmaguire/oauth2-dropbox,pixelfear/oauth2-dropbox