Added surf http client

- updated Makefile
- updated dependencies

reddit/stream.go

@@ -16,6 +16,7 @@ type StreamService struct {
 //   - a channel into which new posts will be sent
 //   - a channel into which any errors will be sent
 //   - a function that the client can call once to stop the streaming and close the channels
+//
 // Because of the 100 post limit imposed by Reddit when fetching posts, some high-traffic
 // streams might drop submissions between API requests, such as when streaming r/all.
 func (s *StreamService) Posts(subreddit string, opts ...StreamOpt) (<-chan *Post, <-chan error, func()) {