sources: add image_url?, page_url?, and profile_url? methods.

Add methods to Source::URL for determining whether a URL is an image
URL, a page URL, or a profile URL.

Also add more source URL tests and fix various URL parsing bugs.

app/logical/source/url/deviant_art.rb

@@ -18,7 +18,7 @@ module Source
   class URL::DeviantArt < Source::URL
     RESERVED_SUBDOMAINS = %w[www]
 
-    attr_reader :username, :work_id, :stash_id, :title
+    attr_reader :username, :work_id, :stash_id, :title, :file
 
     def self.match?(url)
       url.domain.in?(%w[deviantart.net deviantart.com fav.me sta.sh]) || url.host.in?(%w[images-wixmp-ed30a86b8c4ca887773594c2.wixmp.com wixmp-ed30a86b8c4ca887773594c2.wixmp.com api-da.wixmp.com])
@@ -106,6 +106,7 @@ module Source
       # https://images-wixmp-ed30a86b8c4ca887773594c2.wixmp.com/f/fe7ab27f-7530-4252-99ef-2baaf81b36fd/dddf6pe-1a4a091c-768c-4395-9465-5d33899be1eb.png/v1/fill/w_800,h_1130,q_80,strp/stay_hydrated_and_in_the_shade_by_raikoart_dddf6pe-fullview.jpg?token=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1cm46YXBwOjdlMGQxODg5ODIyNjQzNzNhNWYwZDQxNWVhMGQyNmUwIiwiaXNzIjoidXJuOmFwcDo3ZTBkMTg4OTgyMjY0MzczYTVmMGQ0MTVlYTBkMjZlMCIsIm9iaiI6W1t7ImhlaWdodCI6Ijw9MTEzMCIsInBhdGgiOiJcL2ZcL2ZlN2FiMjdmLTc1MzAtNDI1Mi05OWVmLTJiYWFmODFiMzZmZFwvZGRkZjZwZS0xYTRhMDkxYy03NjhjLTQzOTUtOTQ2NS01ZDMzODk5YmUxZWIucG5nIiwid2lkdGgiOiI8PTgwMCJ9XV0sImF1ZCI6WyJ1cm46c2VydmljZTppbWFnZS5vcGVyYXRpb25zIl19.J0W4k-iV6Mg8Kt_5Lr_L_JbBq4lyr7aCausWWJ_Fsbw
       # https://www.deviantart.com/download/549677536/countdown_to_midnight_by_kawacy-d939hwg.jpg?token=92090cd3910d52089b566661e8c2f749755ed5f8&ts=1438535525
       when /^(.+)_by_(.+)[_-]d([a-z0-9]+)(?:-\w+)?$/i
+        @file = filename
         @title = $1
         @username = $2.dasherize
         @work_id = $3.to_i(36)
@@ -113,11 +114,13 @@ module Source
       # http://fc00.deviantart.net/fs71/f/2013/234/d/8/d84e05f26f0695b1153e9dab3a962f16-d6j8jl9.jpg
       # http://th04.deviantart.net/fs71/PRE/f/2013/337/3/5/35081351f62b432f84eaeddeb4693caf-d6wlrqs.jpg
       when /^[a-f0-9]{32}-d([a-z0-9]+)$/
+        @file = filename
         @work_id = $1.to_i(36)
 
       # https://images-wixmp-ed30a86b8c4ca887773594c2.wixmp.com/intermediary/f/52c4a3ad-d416-42f0-90f6-570983e36797/dczr28f-bd255304-01bf-4765-8cd3-e53983d3f78a.jpg
       # https://images-wixmp-ed30a86b8c4ca887773594c2.wixmp.com/f/76098ac8-04ab-4784-b382-88ca082ba9b1/d9x7lmk-595099de-fe8f-48e5-9841-7254f9b2ab8d.png?token=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1cm46YXBwOiIsImlzcyI6InVybjphcHA6Iiwib2JqIjpbW3sicGF0aCI6IlwvZlwvNzYwOThhYzgtMDRhYi00Nzg0LWIzODItODhjYTA4MmJhOWIxXC9kOXg3bG1rLTU5NTA5OWRlLWZlOGYtNDhlNS05ODQxLTcyNTRmOWIyYWI4ZC5wbmcifV1dLCJhdWQiOlsidXJuOnNlcnZpY2U6ZmlsZS5kb3dubG9hZCJdfQ.KFOVXAiF8MTlLb3oM-FlD0nnDvODmjqEhFYN5I2X5Bc
       when /^d([a-z0-9]{6})-\h{8}-\h{4}-\h{4}-\h{4}-\h{12}$/
+        @file = filename
         @work_id = $1.to_i(36)
 
       # http://www.deviantart.com/download/135944599/Touhou___Suwako_Moriya_Colored_by_Turtle_Chibi.png
@@ -125,14 +128,20 @@ module Source
       # http://fc02.deviantart.net/fs48/f/2009/186/2/c/Animation_by_epe_tohri.swf
       # http://fc08.deviantart.net/files/f/2007/120/c/9/Cool_Like_Me_by_47ness.jpg
       when /^(.+)_by_(.+)$/
+        @file = filename
         @title = $1
         @username = $2.dasherize
 
       else
-        nil
+        @file = filename
+
       end
     end
 
+    def image_url?
+      file.present?
+    end
+
     def page_url
       if stash_id.present?
         "https://sta.sh/#{stash_id}"