Inspired by node-throttle module, but acts as a through stream and splits input chunks if required to maintain target speed as close as possible. chunkRate - (default is 10) - output chunk rate. If target speed is 20000 bytes per second and chunk rate is 100, you'll have 100 chunks per second stream, each 200 bytes in size (on average). Note that if input stream is slower then target, chunks are sent immideately at input rate, wich could be higher than target chunk rate. If input is 1000 chunks per second, each 10 bytes shape(20000, 500) should give same 1000 chunk per second x 10 bytes stream.