* Move the source normalization logic out of the post model
and into individual sources' strategies.
* Rewrite normalization tests to be handled into each source's test,
and expand them significantly. Previously we were only testing
a very small subset of domains and variants.
* Fix up normalization for several sites.
* Normalize fav.me urls into normal deviantart urls.
* Normalize spaces to underscores when saving other names. Preserve case
since case can be significant.
* Fix WikiPage#other_names_include to search case-insensitively (note:
this prevents using the index).
* Fix sources to return the raw tags in `#tags` and the normalized tags
in `#normalized_tags`. The normalized tags are the tags that will be
matched against other names.
Fix sources choosing the wrong strategy when the referer belongs to a
different site (for example, when uploading a twitter post with a pixiv
referer).
* Fix `match?` to only consider the main url, not the referer.
* Change `match?` to match against a list of domains given by the `domains` method.
* Change `match?` to an instance method.
Derive the artist name / profile url / page url from the source URLs when
the API response is unavailable because the Tumblr post was deleted.
This fixes the artist finder to work on bad_tumblr_id posts.
* Convert Tumblr commentary to DText.
* Strip extraneous whitespace in links and blockquotes.
* Add newlines after block elements to ensure they're separated from
subsequent blocks.
