Use Set where it makes sense (#35)

A bunch of this array-generating code calls `uniq` which is a great case
for using `Set`. Also, assigning variables isn't the end of the world
and doing so avoids chained allocations and lets us use bang methods
like `reject!`.

Author: jgarber623

lib/webmention/client.rb

@@ -63,13 +63,16 @@ def inspect
     def mentioned_urls
       response = source_url.response
 
-      self.class
-          .registered_parsers[response.mime_type]
-          .new(response.body, response.uri)
-          .results
-          .uniq
-          .reject { |url| url.match(/^#{response.uri}(?:#.*)?$/) }
-          .sort
+      urls = Set.new(
+        self.class
+            .registered_parsers[response.mime_type]
+            .new(response.body, response.uri)
+            .results
+      )
+
+      urls.reject! { |url| url.match(/^#{response.uri}(?:#.*)?$/) }
+
+      urls.to_a.sort
     end
 
     # Send a webmention from this client's source URL to a target URL.

lib/webmention/verification.rb

@@ -61,7 +61,7 @@ def vouch_mentions_source?
     #
     # @return [Array<String>]
     def mentioned_domains(response)
-      mentioned_urls(response).map { |url| HTTP::URI.parse(url).host }.uniq
+      Set.new(mentioned_urls(response).map { |url| HTTP::URI.parse(url).host }).to_a
     end
 
     # @param response [Webmention::Response]
@@ -70,10 +70,11 @@ def mentioned_domains(response)
     #
     # @return [Array<String>]
     def mentioned_urls(response)
-      Client.registered_parsers[response.mime_type]
-            .new(response.body, response.uri)
-            .results
-            .uniq
+      Set.new(
+        Client.registered_parsers[response.mime_type]
+              .new(response.body, response.uri)
+              .results
+      ).to_a
     end
   end
 end