oauth.go
func (o OAuth) RefreshTokens(oldTokens map[string]interface{}) (*oauthTokens, error) {
	refresh_token := oldTokens["refresh_token"].(string)
	return o.GetTokens(refresh_token, "refresh_token")
}
func (o OAuth) RefreshTokens(oldTokens map[string]interface{}) (*oauthTokens, error) {
	refresh_token := oldTokens["refresh_token"].(string)
	return o.GetTokens(refresh_token, "refresh_token")
}
// RefreshTokens refreshes a users existing OAuth tokens