Remove the `image_url` method from source strategies. This method would
return only the first image if a source had multiple images. The
`image_urls` method should be used instead. Tests were the main place
that still used `image_url` instead of `image_urls`.
Also make post replacements return an error if replacing with a source
that contains multiple images, instead of just blindly replacing the
post with the first image in the source.
that's the latest commit made to deviantart files before switching from
the developer API to the Javascript backend from the new "Eclipse"
frontend.
This is necessary because it's basically impossible to download posts
now with the JS backend without being logged in, i.e. having the cookies
from a logged in user, which can't be used for very long even if
exporting them from a browser. You would have to save the cookies
deviantart sends you back via the "Set-Cookie" header in a database
somewhere in addition to the other added complexity.
also
* (temporarily) replace HttpartyCache with HTTParty as it's long been
removed
* fix one case of "last argument as keyword parameter"
* change repository url (5d1a1cc87e)
* remove self-explanatory comment
