Use flickrapi to do the oauth stuff for us

`flickrapi` from here: http://stuvel.eu/flickrapi

4up-photos.py uses a `flickrapi` utility to walk through search results. http://stuvel.eu/media/flickrapi-docs/documentation/#walking-through-a-search-result

4up-faves.py had a bug in the while loop (for me) because it compares an int `page` to str `pages`:
`while not pages or page <= pages`

Fix:
`while not pages or page <= int(pages)`

(The while loop was replaced in 4up-photos by the photo walk.)