WebSocket: fix broadcaster bug on high load

If the broadcaster faces a high load to send out messages since
the program start (e.g: due to local routine that start send
messages like crazy), the broadcaster segfaults due to memory
corruption.

This patchs makes the broadcaster read fixed sizes of frames
and one by one once they arrive.

Signed-off-by: Eduardo Silva <edsiper@gmail.com>
README: update README

Signed-off-by: Eduardo Silva <edsiper@gmail.com>