index, base, js: include google+ login button (not working yet)
all: add license information
Procfile: update command to run the application

We don't need this WSGI file, all Flask objects are already wsgi
applications.
Procfile: bind on localhost only
js/gplus: implement callback to authentication

This callback will ignore failures. In case of success, it will send the
acquired token to the server (next, I will work on the server side).