Reset current_organization_id on logout

[sseerrggii]

Seems that current_organization_id saved in session[:current_organization_id] persist after logout. This generate some problems, I noticed that:

1. I login in mobile app with user in organization 1
2. logout
3. Try to login again but with user that belongs to organizatio 2
4. I login with this user but app shows organization 1 😱

This problem only occurs in the mobile app, I'm not sure if its something from this repo or from https://github.com/coopdevs/timeoverflow-mobile-app