Edited Issue: websocket_client - set_data using istream should have a default option to read until end of stream [152]

codereview comment from Steve:
"Should the len variable default to some value which means read until the end of the stream?"

While setting data on a websocket outgoign message using stream interfaces, have a default option to read to end of stream, instead of asking the user to specify the size of data. Size of data may not be available if user is simply using a producer consumer stream.