README: Use of uber-jar and open jmx
README: Use of uber-jar and open jmx

This update the README to reflect the changes in the maven and with the
updated command line that open the jmx for external connection so the
nodetool will be able to connect to the jmx proxy.

Signed-off-by: Amnon Heiman <ed5fc74c4692051ad0b19749fd7cea6ec2d74b9e@cloudius-systems.com>
Signed-off-by: Pekka Enberg <add4fcd06328a394f0ad91feda7ee057316dc5ed@cloudius-systems.com>

linearregression/scylla-jmx,scylladb/scylla-jmx,linearregression/scylla-jmx,asias/scylla-jmx,asias/scylla-jmx,scylladb/scylla-jmx,scylladb/scylla-jmx