Access to shared portfolio #162

The "share your portfolio" feature implementation has changed and so it doesn't work anymore. I will remove it and I open this issue to track interest for a new implementation.

Apparently, the new implementation will pass the sharing_link_id and optionally the access_code to all API calls. The access_code can be validated with a GET https://api.finary.com/users/me/sharing_links/{SHARING_LINK_ID}/validate?access_code={ACCESS_CODE}