OAuth2 Client:
Wrapper refresh!() accepts same parameter as wrapped function fetch_access_token!().
For some services, it is necessary to send specific individual additional parameters when refreshing the access token, eg. Highrise expects the parameter "type" to be set to "refresh".
Merge pull request #38 from andirayo/master

@sporkmonger:  Added function-paramter to wrapping function in OAuth2-Client