+ Returns a list of Imgur URLs to image files posted to the Reddit SFWPorn network.
+ Won't guarantee that all URLs are valid, but most should be.
r = requests.get(REDDIT_SFWPORN_URL)
j = json.loads(r.content)
+ Tries to download all the images from a passed-in list of URLs into the local directory.
+ Skips any images that exist locally, and pauses 10s between downloads.
urls = reddit_sfwporn_urls()