Fix article ID parsing bug

Since the article ID regular expression wasn't anchored to the end of
the URL, it would grab characters after a / or - that were hex
characters. For example /@user/bacon-123abc would just grab `bac`. Not
great.

This anchors the ID at the end of the string so that it will be more
likely to catch IDs.

src/classes/article_id_parser.cr

@@ -1,7 +1,7 @@
 class ArticleIdParser
   include Monads
 
-  ID_REGEX = /[\/\-]([0-9a-f]+)/i
+  ID_REGEX = /[\/\-]([0-9a-f]+)$/i
 
   def self.parse(request : HTTP::Request)
     new.parse(request)