Update README.md example
Update README.md example

Due to issue https://github.com/influxdb/influxdb/issues/3467, the field key named `user` gives an error. This change prevents users from running into the bug, which will likely be fixed in 0.9.3.
akshayvaidya/influxdb-java,influxdata/influxdb-java,mariusoe/influxdb-java,RaphaelAudet/influxdb-java,jzonthemtn/influxdb-java,mnuessler/influxdb-java,wyzssw/influxdb-java,fernandopeinado/influxdb-java,jordmoz/influxdb-java,mariusoe/influxdb-java,SpanningCloudApps/influxdb-java,RaphaelAudet/influxdb-java,influxdata/influxdb-java,jzonthemtn/influxdb-java,influxdb/influxdb-java,SenseTecnic/influxdb-java,caoli5288/influxdb-java,mistsys/influxdb-java,piyush82/influxdb-java,Kindrat/influxdb-java,marsishandsome/influxdb-java,itachi90/influxdb-java,ind9/influxdb-java,fernandopeinado/influxdb-java