Add support for streaming instead of serving from disk

[airtonix]

You'll have to excuse me if I mis understood how connect-compiler should work, but perhaps an option should be made available that skips writing/serving anything from disk and instead streams it directly.

If we all understand that assets should be compiled, minified, hashed, gzipped and bamboozled in production, then I hope we can understand that streaming compiled assets directly during development would eliminate any problems of stale files.