Fix HTTP::Request#headline to allow two leading slashes in path

lib/http/request.rb

@@ -154,7 +154,7 @@ def headline
         if using_proxy? && !uri.https?
           uri.omit(:fragment)
         else
-          uri.omit(:scheme, :authority, :fragment)
+          uri.request_uri
         end
 
       "#{verb.to_s.upcase} #{request_uri} HTTP/#{version}"

spec/lib/http_spec.rb

@@ -41,6 +41,12 @@
       end
     end
 
+    context "with two leading slashes in path" do
+      it "is allowed" do
+        expect { HTTP.get "#{dummy.endpoint}//" }.not_to raise_error
+      end
+    end
+
     context "with headers" do
       it "is easy" do
         response = HTTP.accept("application/json").get dummy.endpoint