Import `(readable-stream).Transform` and use stream-browserify in browser

Please see this reduced test case of an oddity I ran into this evening. I could really use your advice.

https://github.com/gobengo/chronos-stream-dependant

Without this patch, whenever I would require through2, it would break completely separate parts of my dependency tree that were using readable-stream.

If you look at this and help out, thank you so much!

(great lib)