Fix multi-method routes to append '(.:format)' only once

Because the same path string is used for each loop when the routes
are being built, appending the string using `<<` modifies the original,
causing multiple '(.:format)' strings to be appended. This fixes the
behavior, resulting in the proper path output.

Signed-off-by: Evan Owen <kainosnoema@gmail.com>

lib/grape/endpoint.rb

@@ -85,8 +85,7 @@ def prepare_path(path)
       parts << ':version' if settings[:version] && settings[:version_options][:using] == :path
       parts << namespace.to_s if namespace
       parts << path.to_s if path && '/' != path
-      parts.last << '(.:format)'
-      Rack::Mount::Utils.normalize_path(parts.join('/'))
+      Rack::Mount::Utils.normalize_path(parts.join('/') + '(.:format)')
     end
 
     def namespace

spec/grape/api_spec.rb

@@ -230,6 +230,10 @@ def app; subject end
         "hiya"
       end
 
+      subject.endpoints.first.routes.each do |route|
+        route.route_path.should eql '/abc(.:format)'
+      end
+
       get '/abc'
       last_response.body.should eql 'hiya'
       post '/abc'