Coverage for direct gfycat links that redirect to redgifs. The redirect through the sites themselves are broken but this fixes that.
Coverage for o.imgur links and incorrect capitalisation of domains in download_factory.
Changed tests for direct as gfycat is handled by the gfycat downloader.
fix pornhub test as the previous video was removed.
Attempt to fix#724
Narrows down characters available to extensions in the regex. Outside of 3 and 4, the only extensions that I can think of this doesn't hit are bz2 and 7z (which wasn't caught before).
Standardizes shebang and coding declarations.
Coding matches what's used by install tools such as pip(x).
Removes a few init files that were not needed.
Cover edge cases that shouldn't ever happen but probably will sometime.
Also included Imgur changes to cover similar situations of malformed/redirected links.
Erroneous .gifv extensions such as .giff or .gift resolve to a static image and are downloaded by the direct downloader. (ex: https://i.imgur.com/OGeVuAe.giff )