Explicitly initialize isClosed for readability; increase recv buffer to 4MB (helps with video streaming)
Fixed: HttpProxy.Close() left existing local->proxy persistent connections open. Browsers kept trying to use these connections, which would always return errors even when the underlying tunnel was gone. HttpProxy now tracks open connections and closes them all on Close(). Also force close local->proxy persistent connections immediately when the round trip fails.
Merge pull request #17 from rod-hynes/master

Bug fixes while testing meek [see commit messages]