In recent PopIt, 'organisation' is now spelled 'organization'
The collection is now referred to as persons
Ignore backup files from common text editors
Rename the popit module to popit_api to avoid a name clash

Unfortunately, the name popit at the top level clashes with
popit-django, which is more widely used at the moment.  So,
rename the popit module to popit_api.
Update the README for the current popit-api