add support for stream_read_delta() and stream_write_delta()
add support for stream_read_delta() and stream_write_delta()

Signed-off-by: Javier Luraschi <cb1ef5c9ecf67cdff88d1849c5ec0d20c1752721@hotmail.com>

rstudio/sparklyr,rstudio/sparklyr,rstudio/sparklyr,rstudio/sparklyr