docker: update readme
docker: update readme

Changes the second docker-compose command to "run" instead of "up",
since this was failing for several people. Also removes the use of
the --num_conf flag to lncli openchannel, as this was removed in
0dfe733.

aakselrod/lnd,ddustin/lnd,LightningNetwork/lnd,ddustin/lnd,LightningNetwork/lnd,aakselrod/lnd