sources: fix 4chan URL parsing.

Add support for is2.4chan.org image URLs and various old URL formats.

test/unit/sources/four_chan_test.rb

@@ -69,5 +69,21 @@ module Sources
         )
       end
     end
+
+    should "Parse 4chan URLs correctly" do
+      assert(Source::URL.image_url?("https://i.4cdn.org/vt/1668729957824814.webm"))
+      assert(Source::URL.image_url?("https://i.4cdn.org/vt/1668729957824814s.jpg"))
+      assert(Source::URL.image_url?("https://is2.4chan.org/vg/1663135782567622.jpg"))
+      assert(Source::URL.image_url?("http://is.4chan.org/vp/1483914199051.jpg"))
+      assert(Source::URL.image_url?("http://images.4chan.org/vg/src/1378607754334.jpg"))
+      assert(Source::URL.image_url?("http://orz.4chan.org/e/src/1202811803217.png"))
+      assert(Source::URL.image_url?("http://zip.4chan.org/a/src/1201922408724.jpg"))
+      assert(Source::URL.image_url?("http://cgi.4chan.org/r/src/1210870653551.jpg"))
+      assert(Source::URL.image_url?("http://img.4chan.org/b/src/1226194386317.jpg"))
+
+      assert(Source::URL.page_url?("https://boards.4channel.org/vt/thread/37293562#p37294005"))
+      assert(Source::URL.page_url?("http://boards.4chan.org/a/res/41938201"))
+      assert(Source::URL.page_url?("http://zip.4chan.org/jp/res/3598845.html"))
+    end
   end
 end